The genus Maihueniopsis comprises plants which forms small to large mounds of many stems. These are mostly dense, but sometimes loosely branched. The stems are usually gray-green, with branches arising basally, from the side, or toward the tip. Rarely, the branches grow together (M. molfinoi). The plant body is soft and the flesh contains much mucous. Branches are at first barrel shaped, later more conical, 1.5–9 cm long and 1.5–3 cm across. Young branches are tuberculate, later smooth or slightly depressed at the areoles. The areoles are round or slightly elongated, small, often sunken and evenly distributed over the branch. Lower areoles have bundles of glochids, with one or more central spines, which are round to flattened, and a few shorter spines, which are often deflexed. Spines are absent on lower areoles. Flowers are typically Opuntia-like, with a yellow perianth.

Fruits are reverse club-shaped to ovate, barely tuberculate, and colored green to yellow. They are covered with white, wooly areoles, which mostly bear glochids, and frequently fine spines. Usually thick walled–some Chilean species are thin-walled–the fruits are filled with slimy, acidic pulp.

Seeds have a thin funicular envelope, are mostly flattened, and can appear wooly or smooth.

Helmut Walter (co-author with Adriana Hoffmann, in the second edition of Cactáceas en la flora sylvestre de Chile 2004) and I joined forces to try and solve the inter-relationship of the Chilean Maihueniopsis.

Introduction

David Hunt's treatment of Maihueniopsis in the New Cactus Lexicon leaves many questions unanswered. Hunt recognizes M. archiconoidea, M. conoidea and M. glomerata for the Chilean Maihueniopsis species. M. glomerata is described as coming from Argentina with somewhat doubtful type localities, and even worse descriptions. It is possible that M. glomerata of Argentina co-evolved with M. glomerata of Chile. This is a review of our field data.

Ritter's studies of the seeds of the Chilean Maihueniopsis separated them as wooly and non-wooly. Our current field-work data supports this concept, with some minor modifications. The terms wooly and non-wooly are, however, somewhat misleading. Buxbaum (1950) reported that the pulp in Opuntia fruit consists of many hairs originating from the pericarpel, funiculi, and funicular envelope. Closer examination of dry seeds of Maihueniopsis shows that the non-wooly seeds have very short hairs as opposed to long hairs on the wooly seeds. We have also added a fruit characteristic where species with non-wooly seed do not have robust spination on the floral umbilicus areoles, while fruit with wooly seed do. On our recent expeditions, we were also able to add floral data to many of the known populations (Fig. 1).

1

Distribution map of the genus Maihueniopsis in Chile.

Iliff also writes that Ritter mis-interpreted Philippi's description for M. atacamensis. We agree with this. Ritter's collections of M. colorea and camachoi, from NE of Copiapó, are clearly two different species: M. colorea, growing between km 70 and km 100, and at about 2000 m altitude, has wooly seeds and spiny fruit. The plants at km 130, that are at about 3000 m altitude, have non-wooly seeds and naked fruit, placing the higher elevation plants into the M. atacamensis Phil. group.

The species with non-wooly seed in this treatment are: M. archiconoidea, M. atacamensis, M. conoidea and M. leoncito (including M. reicheana). Species with wooly seed are M. camachoi, M. colorea, M. crassispina, M. domeykoensis, M. grandiflora, and M. wagenknechtii. M. ovata consists of several populations which are sterile and never produce seed, so it is not known if they are wooly or not.

Maihueniopsis atacamensis

Rudolpho Philippi described Opuntia atacamensis in “Die Reise durch die Wueste Atacama” (1864). Philippi listed several localities where he found opuntias, but herbarium records do not exist. In his description of O. atacamensis, he gave three localities with estimated latitude wherein he considered the range of the species. In his other writings, however, he reports O. atacamensis from much further south and as far north as San Bartolo. One can only conclude that the range is larger than Philippi recorded in the protolog.

Werdermann's collection #1050, from near Aguada de Varas, was designated as neotype by Iliff (2001) for Philippi's O. atacamensis. Iliff also reports that Ivan Johnston collected a similar plant near Sierra San Miguel which is much further south (Fig. 2). Plants collected from Sierra San Miguel had non-wooly seed, naked fruit, and umbilicus areoles without spines, suggesting some relationship to M. atacamensis.

2

FK 1164, M aff. atacamensis, on the road from Puquios to the West side of Salar de Maricunga at 2760 m. A similar population, FK 1165, exists at 3100 m. This is the area where Ivan Johnston collected a similar plant to Werdermann's neotype. near Sierra San Miguel.

BB884 (Figs 3, 4) was collected by Marcello Rosas, Senior Botanist at the INIA seed bank, near Mina Plata de Sopa, which is south of Werdermann's collection near Sierra de Varas, and north of the Ivan Johnston site of Sierra San Miguel. It is close to M. atacamensis. James Iliff, in Studies in the Opuntioideae 2002, drew a picture of the seed of Werdermann's herbarium specimen of M. atacamensis, which those in Figs. 5 & 6, resemble. The illustration does not show the hole, although the obscured funiculum is mentioned. This opening does not exist in any of the group with wooly seeds. Fig. 7 shows details of the seed surface of BB84, contrasting strongly with that of M. crassispina, a typical wooly-seeded species, in Fig. 8. FK1170 (Fig. 9) is what Ritter believed to be part of M. camachoi but clearly is part of M. atacamensis Werdermann not M. atacamensis Ritter, due to its having a spineless fruit and non-wooly seed surface. In addition, M. camachoi has reddish-brown stigma lobes, which FK 1433, from the same locality, does not (Fig. 10). Ritter mentions that seed from plants in this population have a pronounced funicular girdle, as is indeed observed for these plants (Fig. 11).

3

BB884 INIA, aff. M. atacamensis.

4

Detail of branch and oval fruit of BB884. The floral umbilicus is without spines.

5

Seed of BB884 showing the surface. A large round opening, near the hilum, is also apparent. This opening exists on all the non-wooly seeds except M. conoidea.

6

Removal of the funicular envelope exposes the seed surface for further study. It also shows that the envelope is thin, typical for all of the Chilean Maihueniopsis.

7

Non-wooly seed surface of BB884 at 40× showing the apparent lack of hairs. The hairs that are present during early fruit maturing completely shrink to the seed surface.

8

Wooly seed FK 1160 M. crassispina at 40×, showing a multitude of long hairs.

9

FK 1170 M. aff. atacamensis from Cuesta Francisco at 3200 m, about 130 km from Copiapó.

10

FK 1433 (same locality as above, but years apart) showing the yellow flower with green stigma lobes. M. camachoi has reddish-brown stigma lobes.

11

Seed of FK 1170, from Cuesta Francisco, has the micropylar hole. It also shows the very pronounced funicular girdle as described for this population by Ritter.

Maihueniopsis conoidea

This species (Figs. 12–17) is distributed from San Pedro de Atacama to Santa Barbara. It can often be found amongst plants of M. camachoi and Cumulopuntia boliviana subsp. ignescens. It has non-wooly seeds which lack the micropylar hole and are not round-lenticular, but rather almost triangular (Fig. 16). The seed hairs are intermediate between M. crassispina and M. BB884.

12

M. conoidea FK 330, from slopes near Puritama at 2970 m.

13

M. conoidea FK 330, with an unusually large tap root.

14

Flower section of M. conoidea, showing the elongated pericarpel.

15

The fruit of M. conoidea is almost half the size of that of M. atacamensis

16

The seed of M. conoidea does not have a micropylar hole, as does M. atacamensis, and it is more or less angular, not lenticular.

17

FK 1187 from near Volcan San Pedro, on the road from Calama to Olargue, at 3600 m. Seeds suggest an affinity to M. conoidea.

Maihueniopsis leoncito

Mario Lobos of INIA and Susan Aument of Brooklyn Botanical Garden were collecting material for the seed bank (Figs. 18–21). The goal was to collect 10,000 seeds because they were to be shared with Kew Botanical Gardens. There are about 50–60 seeds per fruit (Fig. 22); collecting fruit was stopped when we had about 200. There is some correlation of the growth of the grasses to the presence of this species. The branches are short-oval, 2–3cm diameter, to 5 cm long; the spines are flattened and more or less upright (Fig. 19).

18

M. leoncito FK 1168 near Cerro Cadillal at 3900 m. The grass serves as guanaca (wild Camelid) food and, as the habitat picture shows, M. leoncito of this population is the same color as the grasses, suggesting that they are not easily distinguishable by the guanacas.

19

Stems of M. leoncito.

20

A form of M. leoncito with reflexed spines.

21

Flower of FK 1286-B. All the flowers of Maihueniopsis with non-wooly seeds have green stigma lobes, while those with wooly seeds have mostly reddish stigma lobes.

22

The fruit of FK 1168 is thick walled, without clusters of stiff spines from the areoles of the flower's umbilicus.

In search of other populations of M. leoncito, we found several others (FK 1284, 1285 and 1286) north east of La Gardia, about 45 km north of FK 1168. As Figs 20–21 show, the spines are not upright, but are more reflexed as observed in M. archiconoidea. The seed are not covered by white hair-like structures, but rather by a dense micro-fiber-like layer (Figs. 24–25).

23

The entry of the micropyle is a hole at the side of the seed. M. archiconoidea has similar seeds.

24

The seed with the outer layer, containing the hair, was removed, showing a striate-like funicular envelope that covers the seed.

25

After removal of the funicular envelope, one can clearly see the funicle wrapped around the seed.

Maihueniopsis reicheana

This species was described by Espinosa in 1941, and grows about 200 km south from Cadillal in the area of Banos de Toro at 3200m (Fig. 26–27¹). An old picture taken by Espinosa of this plant shows it to have yellow flowers. There is an excellent herbarium sheet by Espinosa at the Museum of Natural History in Santiago, Chile.

26

Opuntia reicheana (syn. M. glomerata) FK 1157.

27

A view of the flattened spines, which are deflexed, not as in M. leoncito.

Maihueniopsis archiconoidea

Figs. 28–30 show M. archiconoidea. Its branches, with deflexed, flattened spines, are much smaller than M. leoncito.

28

FK 1159 M. archiconoidea, near Conay at 2000 m.

29

M. archiconoidea FK 1159, near Conay at 2000 m. showing the deflexed, flattened spines.

30

M. archiconoidea fruit. Photo by H. Walter.

Maihueniopsis camachoi

Espinosa also described M. camachoi and gave the type locality as the area between Calama and San Pedro. In this population, it is quite common that very large plants die in the center, forming, more or less, a ring of more than 2 meters diameter (Fig. 31). Ritter's description of M atacamensis appears to be based on material belonging to M. camachoi. Fig. 32 shows the typical branching pattern, with new branches forming from the side, never from the apex. Spines arise from areoles in the upper 2/3 of the branch. M. camachoi has typical Maihueniopsis flowers, with reddish stigma lobes (Fig. 33). The fruit is thin walled, with clusters of stiff spines protruding from the areoles on the edge of the flower umbilici (Fig. 34). The seeds are lenticular, and covered by trichomes (Fig. 35). The seed surface is comprised of cells with 6–10 U-shaped anticlinal border undulations (Fig. 36).

31

M. camachoi FK 328 growing between Calama and San Pedro de Atacama at 2900 m.

32

Each branch is 2–3.5 cm in diameter and 4–6 cm long.

33

M. camachoi FK 328 M. camachoi flowers have red-brown stigma lobes; so does M. wagenknechtii, but the flowers of M. domeykoensis and M. grandiflora have green stigma lobes. Green stigma lobes are also found in M. leoncito and M. conoidea.

34

The fruit of M. camachoi FK 1116 is thin-walled and filled with pulp surrounding the seed. Areoles are present on sides of the fruit, with a concentration on the floral umbilicus rim. The floral umbilicus is wide and shallow.

35

The seeds of M. camachoi are almost perfectly round.

36

SEM showing seed cells at 400×. The almost isodiametric cells, with the U-shaped projections, fit to mimic a jigsaw perfectly.

Maihueniopsis colorea

M. colorea, growing further south, is part of the M. camachoi group. Fig. 37 shows a plant from Ritter's type locality between 70–100 km from Copiapó and about 700 m lower in altitude than FK 1433 (Fig. 10). The flower (Fig. 38) has yellow to slightly reddish stigma lobes, with a few areoles on the pericarpel and tube, the uppermost of which form spines. A desiccated fruit has stiff spine clusters on the flower's umbilicus. The seed is wooly, and without a micropylar hole. Figure 39 shows that the cells of the testa show far fewer undulations per cell than for M. camachoi (Fig. 35).

37

FK 1431 M. colorea.

38

FK 1431 M. colorea, stigma lobes are yellow to slightly reddish, a few areoles appear on the pericarpel and tube. Spines form on the upper areoles. The seed is wooly and without a micropylar hole.

39

The scanning electron micrograph of M. colorea seed show cells with fewer undulations compared to M. camachoi.

Maihueniopsis crassispina

Figure 40 shows this taxon at Quebrada Maitencillo, 300 m, where the flowers have a reddish tint, and red stigma lobes (Fig. 41). Additional populations were observed north and also south of Mina El Algarrobo. The fruit (Fig. 42) has very thick spines arising from the flower-umbilicus areoles.

40

M. crassispina FK 1403.

41

M. crassispina HW, ex habitat from the population of FK 1403, SW of Maitencillo. M. crassispina has red stigma lobes and reddish color, while the more southerly-growing M. domeykoensis has green stigma lobes and yellow flowers.

42

A dehydrated fruit of M. crassispina FK 1160.

Maihueniopsis domeykoensis

This species (Fig. 43) grows further south than M. crassispina, and differs in having yellow flowers with green stigma lobes (Fig. 44).

43

M. domeykoensis FK 1023, west of Domeyko at 600 m altitude.

44

M. domeykoensis flower. Photo by H. Walter.

Maihueniopsis wagenknechtii

The branches of M. wagenknechtii (Fig. 45) have almost double the number of areoles observed in M. crassispina, M. domeykoensis, or M. grandiflora. The spiny areoles also extend to the base of the branch. The flower has stigma lobes are purplish (Fig. 46).

45

FK 1373 M. wagenknechtii north east of Trapiche at 1600 m altitude.

46

M. wagenknechtii, showing purplish stigma. Photo by H. Walter.

Maihueniopsis grandiflora

This plant differs from the other species of Maihueniopsis by virtue of its distinctive white spination (Fig. 47). The flowers have green stigma lobes (Fig. 48), though those from the population from above Huanta (Fig. 49) are reported to be red. The seeds (Fig. 50) are larger than most other wooly-seeded species.

47

Maihueniopsis grandiflora FK 1234, north east of Tres Cruzes, at 2000 m altitude.

48

M. grandiflora FK 1234 flower.

49

M. grandiflora FK 1097, from above Huanta at 1800 m. This population is reported to have reddish flowers and reddish stigma lobes, but could not be confirmed.

50

The seed of M. grandiflora is larger than most other wooly-seeded Maihueniopsis.

Maihueniopsis ovata

Three populations of M. ovata were found by Ritter in Chile. Fig. 51 shows FK 1220, from El Volcan. The plant subsequently flowered in Helmut Walther's collection (Fig. 52).

51

Maihueniopsis ovata FK 1220 at 1900m, is sterile.

52

M. ovata flower bud, photographed in Helmut Walter's collection.