DEPARTMENT OF BOTANICAL RESEARCH. 73 



Two cylindro-opuntias, Opuntia arbuscula and 0. neoarbuscula, of 

 nearly similar subaerial habit, were found to possess in the former 

 fibrous roots and in the latter fleshy roots, under natural conditions. 

 The two species were treated in a similar manner and both had unac- 

 customed depth of soil and supply of water. The development of both 

 species, however, was not changed, as regards the qualities named. 



Opuntia spinosior, 0. vivipara, and 0. discata were grown under 

 relatively favorable conditions as to soil-depth and water-supply, 

 and certain specimens were placed where their roots projected in 

 sand. The most striking result was a nearly or total suppression 

 of the absorbing system of the roots in certain cases, by which the 

 modified systems closely resembled the generalized type. An abund- 

 ant supply of water thus operates to lessen the differentiation of the 

 roots and also to bring about a somewhat deeper placing of the 

 root-system. 



For the purpose of bringing about the deepest possible root pene- 

 tration of normally shallowly rooted species, mainly the cacti, several 

 plants were caused to grow in glass or metal tubes of various sizes, 



Jatropa cardiophylla, which in nature has fleshy roots within 5 

 cm. of the surface, was induced to send roots to a depth of 43 cm. 



Fouquieria splendens has a root-system which, in a measure, is 

 intermediate between that of Franseria and that of the cacti. The 

 roots usually penetrate less than 37.5 cm., but in tubes transplanted 

 specimens were seen to send roots as deeply as 1.1 meters. Seed- 

 lings of the species, 7 months old, formed a main root 47 cm. long. 



Opuntia arbuscula, whose anchoring roots usually attain a depth 

 of less than 30 cm. and whose absorbing roots lie as near the surface 

 as 1.5 cm., formed roots 1.12 meters in length in glass tubes. The 

 roots of 0. versicolor, which also are usually shallowly placed, formed 

 a main root 78 cm. long. 



The Root-Characters of Trees Grown in the Coastal Climate of California, 

 by W. A. Cannon. 



Studies were made of the root-systems of several native trees of 

 the coastal region and adjacent valleys. The results indicate that 

 the species have each a characteristic type of root development and, 

 further, that each kind of root-system has especial adjustment to the 

 conditions of soil-moisture. The roots may be very extensive later- 

 ally, and especially they may penetrate relatively deeply, as in the 

 case of Quercus lobata, or, on the other hand, as in Quercus agrifolia, 

 they may lie for the most part close to the surface of the ground 

 and thus be in position to advantage directly from the rains. In 

 the last species the more deeply penetrating portion of the root- 

 system is relatively unimportant and probably does not usually 



