MISCELLANEOUS SPECIES. 41 



9 



on dry slopes and mesas. The analyses are not encouraging, but are 

 of interest in that they demonstrate positively the presence of rubber 

 in this genus of plants and show that the leaves carry a higher per- 

 centage than the stems. Perhaps the most significant result is the 

 finding of 1.3 per cent in a mixture consisting of a stem with all of it3 

 leaves (372). 



Cryptostegia grandiflora.— This is a native of the Old World, 

 probably of Indian origin, and as such scarcely falls within the scope 

 of the present survey. A sample was sent by a correspondent of Los 

 Angeles, California, with the statement that it came from Lower 

 California. If this is correct, the sample was from a cultivated speci- 

 men. The plant has been used in India for its caoutchouc, but not to 

 any considerable extent. It is a woody climber that is often grown in 

 greenhouses for its showy blue flowers and endures the out-of-doors 

 temperature of Florida. The sample mentioned (935) was found to 

 carry 1 per cent of rubber in the stems and 5.1 per cent in the foliage. 

 These determinations are for pure rubber and are computed on the 

 basis of dry weight. The product so obtained is shinv, very elastic, 

 and may be piilled out into threads an inch long. 



Jatropha cardiophylla. — The jatrophas are shrubs and trees of the 

 warmer parts of both hemispheres. The genus, which belongs to the 

 Euphoriacese, or spurge family, is well represented in Central America 

 and Mexico, a few species occmring also in the southwestern part of 

 the United States. J. cardiophylla is a shrub 1 to 4 feet high which 

 grows on the very dry hills of southern Arizona send northern Sonora. 

 It seems to be especially common on the lower slopes of the Santa 

 Catalina Mountains. The leaves, which appear only after the simimer 

 rains, are broadly ovate or rhombic, with a truncate or cordate base, 

 and are 0.5 to 1.5 inches wide. The plants readily produce new stems 

 when pollarded and are easily propagated by cuttings. A collection 

 (993) made on Tumamoc Hill, Tucson, Arizona, February 21, 1920, 

 was found on analysis to carry 3 per cent of rubber in the stems. 

 Further examinations should be made of this spiecies, as well as of all 

 others of the Southwestern States. 



Hymenoxys floribimda utilis (Colorado rubber plant, or Pinguay). — 

 This composite herb has been already discussed (p. 9). Two collec- 

 tions have been analyzed during the course of the studies. One of 

 these (931), from Las Vegas, New Mexico, was divided into two 

 parts. That portion consisting of the root and the old stem-bases 

 contained 3.6 per cent of rubber. The other portioa^ consisting of 

 the main stems and leaves, contained 0.84 per cent. The other col- 

 lection (947) was made at Buena Vista, Colorado, August 1, 1920. 

 In this ihe whole plant was ground up and the mixture of root, stem, 

 and leaf yielded 0.9 per cent of rubber. All of these analyses were by 



