282 The Botanical Gazette. [May, 
marked secondary changes in the endodermis and cortex, 
which do not occur in the root of either; in the second the 
development of the tuber is accompanied by the formation 
of secondary xylem bundles, and of a large medulla, the cen- 
tral portion of which undergoes a marked sclerosis: features 
entirely absent from the root. Further, the cambiform rays of 
1. biternatum are formed opposite the two secondary bundles 
and extend half the distance to the cortex terminating ina 
strand of woody cells originating in the perigycle, while in 
/, occtdentale the cambiform rays are developed opposite the 
four or five primary bundles only, and extend only part way 
to the woody strands in the pericycle. 
So far as the physiological features of the tubers of the last 
named species have come under observation, they show a 
close similarity to those of the first. The parenchymatous 
cells from the tubers of plants beginning to bloom March 24th 
gave the globular aggregations on the application of strong 
alcohol. A few weeks later they contained numbers of gran- 
ules reacting as ‘“‘red starch.” The cortical cells were also 
filled with reddish brown drops of oil, and the outer layer 
was infested with a number of hyphae. The presence of 
sclerenchyma in the medulla and in consequence in the 
tuber alone is somewhat remarkable, and seems entirely un 
explainable by any of the accepted principles of mechanical 
induction; a fact more clearly apparent when it is remem 
bered that the tubers are clustered in a compact mass in such 
Position as to be incapable of receiving strains of any moment. 
Neither may inferences of value be deduced from a considet- 
ation of the absence, presence, or varying disposition of the 
sclerenchymatous tissues in the roots of the closely related 
genera. 
University of Minnesota. 
