ROSE — MEXICAN A N I » CENTRAL AMERICAN PLANTS. 



Purpus, as ;i guide, about twenty species were studied. Here on the 

 dry white chalky plain are found many striking forms. One of the 

 most interesting of these is Mdmillaria angularis Link & Otto, form- 

 ing great clumps consisting of many individuals (PL XVI). Here is 

 also found a giant Echinocactus ( /-'. ingensf), the flesh of which is 

 much employed in making a highly prized confection. The plant 

 grows to be sometimes as much as 2.4 meters tall with a diameter of 90 

 to L20 cm. 'The body is cut into sections resembling American ch< 

 about 60 cm. in diameter and 15 to 20 cm. thick, and these are sent to the 

 candy factory where they are boiled with sugar and made into a candy 

 or "dulce" somewhat resembling preserved citron (PI. XVII). In 

 the same region Opuntia imbricata, 0. tunicata (El. XVII), 0. kleinae, 

 and other Opuntias were abundant, and here we found a natural hybrid 

 between Opuntia microdasys and another Opuntia which has not been 

 specifically identified. Both species were growing near the hybrid. 

 While 0. microdasys is a low, pubescent, spineless species, the other 

 parent is tall, glabrous, and spiny, and the hybrid is somewhat inter- 

 mediate in size and without pubescence or spines. So far as my 

 observation goes natural hybrids are not common among the Cacta- 

 ceae. 



Another very interesting cactus desert which we visited is situated 

 around Tehuacan. It is remarkable especially for the great display of 

 tree species belonging to Cereus, Pilocereus, Cephalocereus, and 

 "Opuntia. The cactus species of all genera seen here numbered 22. 



Two species of Echinocactus (E. flavescens, /:'. robustus (PI. XVI)) 

 form great clumps, very much larger than any 1 had ever seen before. 

 In the case of /:'. robustus it was not uncommon to see masses 1 to L.3 

 meters high and 3 meters in diameter, and in one example nearly 5 

 meters in diameter. Those masses must have contained hundreds, if 

 not thousands, of individuals. A photograph of /*/. robustus is here 

 reproduced. 



On the hills east of the town are great forestsof the huge Cephalo- 

 ,-, n us m.acrocephalu& (PL XLIII, facingp. L26), which in many respects 

 resembles the much better known Cephalocereus senilis. Unlike the 

 latter, however, it develops a very woody trunk. Another striking 

 species is Pilocereus fulviceps (PI. XVIII), which has a short, stout, 

 woody trunk and hundreds of nearly erect branches reaching a height 

 of 12 to 15 meters. These branches set very close together and form 

 a cylindrical ma--, not infrequently ■> meters in diameter. 



Pilocereus chrysomallus^ which grows to the height of -± t<> "» meter-. 

 is a common plant, while ( \ n us hoUianus (PI. XIX) is so common a- to 

 he used a- a hedge plant. It- fruit i- a- large as a gooseegg. Another 

 Uereus near C. stellatns (PI. XX) i- very common and furnishes fruit 

 for the market. Escontria chiotitta (PI. XLIII. facingp. L26) i- -till 



a See p. 126. 



