Votes on California Plants. -I17 
out the year without the production of tubers. When, however, by 
reason of the drying of the soil as summer comes on, the growth of 
the plant is checked, the annular process of the nodes rapidly in- 
creases, becoming eventually an irregular spheroidal tuber, some- 
times a quarter of an inch in diameter. The leaves now turn yel- 
low and wither away, the substance of the internodes is absorbed 
and they decay, and the tubers alone remain to produce a new 
growth with the coming of another wet season. The tubers consist 
of an aggregation of starch cells contained in a thin cuticle and are 
without odor or taste other than the peculiar starchy flavor of raw 
potatoes. 
While, as has been said, there is an apparent difference in the 
manner in which the tubers are produced by the Eastern and the 
Western species, a closer examination shows that they are essen- 
tially the same. In the latter case they are enlargements of the 
nodes of the stolons, while in the former they are terminal at the 
extremity of thread-like stolons emitted by the superficial runners. 
But, as Mr. Holm has pointed out, the thready stolons are merely 
modifications of the creeping stems, as is shown by their nodular 
scales which replace the normal leaves. The terminal tuber itself 
is an agglutination of two or more enlarged nodes, as is indicated 
by the bracts at the more enlarged portion, the less swollen part 
representing the internode, while the bud at the apex shows that the 
growth of the stolon has simply been arrested. From this it results 
that the form of the tuber of H. Americana is oblong, or fusiform, 
while in the Western species it is spherical. Moreover, in H. pro-. 
“ifera all the internodes perish, while in the other species a single 
one is shortened and enlarged, and makes a part of the tuber. To 
the tubers of the former plant, also, the scales and the terminal bud 
are lacking, the first because the leaves which they represent have 
developed and decayed, and the latter because the tubers do not 
include the germinal apex. 
Furthermore, the production of tubers in A. Americana is regu- 
lar, and all the other parts of the plant are destroyed by the rigors 
of winter. In H. prolifera, at least in this mild climate, it is occa- 
sional, and dependent upon the supply of moisture, so that they are 
produced only when the plant is unable to continue its growth. 
This special provision for its preservation is the more remarkable 
since our species is an abundant seed producer. 
