1901 | BRIEFER ARTICLES 127 
fruited in it. In peptone the fungi grew rapidly and luxuriantly, 
proving it to be a favorable source of nitrogen.— Mary H. Smiru, 
Botanical Department, Cornell University. 

NON-SEXUAL PROPAGATION IN OPUNTIA. II. 
A VERY interesting Opuntia which has recently come to my notice 
in studying the various propagative methods of the Cactaceae is O. 
arbuscula Engelm., a small, more or less arborescent form, densely 
branched, and reaching a height of about 15. This plant sets an 
abundance of fruit which appears to mature well, but which upon 
examination is found to contain very few good seeds. So laden is the 
plant with its fruit that its branches, as a rule, bend over so as almost, 
if not quite, to touch the ground, In this position there takes place a 
process analogous to “layering,” new shoots of an apparently primitive 
character arising from the decumbent branches, which also give off 
roots into the soil. The same formation of primitive shoots occurs in 
joints detached from the parent plant. This is also true of fruits, from 
the sides of which both stems and roots may often be found forming, 
so often, in fact, that this must be regarded as the rule rather than the 
exception. We have here the case of a structure, modified primarily 
for sexual purposes, turned finally to use in a non-sexual way, to 
accomplish, broadly speaking, the same end. 
Still another method of propagation, perhaps not very common, 
yet apparently not infrequent with this species, is by the formation of 
adventitious shoots on the roots. The roots are, in this form as in the 
majority of the Cactaceae, divided into two systems, as already described.’ 
On the absorptive roots, which run just below the surface, there arise, 
at some distance from the main plant, adventitious shoots of a char- 
acter far more primitive than those formed on fruits or fallen joints. 
The leaves of these shoots are in some cases over 10" long, green, and 
succulent. By the time these shoots reach the height of about 2, the 
root connecting them with the parent plant dies, thus leaving them 
independent at an early stage. 
The distribution of this species is very well defined. It occurs 
almost exclusively in those slight depressions in the plain, which in 
time of hard rains are washed by broad and shallow streams of surface 
* Bor. Gaz. 30 : 348 seg. 1900. 
