NOTES ON CALIFORNIA PLANTS. 
2S 
TUBERIFEROUS ROOTS OF HYDROCOTYLE AMERICANA Kellogg. 
BY S. B. PARISH. 
Three of the North American species of Hydrocotyle within re- 
cent years have been ascertained to be tuberiferous. Attention was 
first directed to this character in HW. Americana by Dr. George 
_Vasey,* and subsequently these organs were thoroughly studied 
and described by Mr. Theodore Holm.t Recently Dr. Coulter, in 
characterizing H. umbellata and H. prolifera, states that their roots 
are tuberiferous.{ No account, however, is given of the manner 
in which the tubers of these two species are produced. 
The method of their development in ¥. prolifera is quite differ- 
ent from that of the same organs in H. Americana, although in fact 
essentially similar. The latter species grows by means of terres- 
trial runners from which arise the flowers and leaves and whose ax- 
ils develop slender subterranean stolons, consisting of a few inter- 
nodes, bearing at each node a scale-like leaf and terminating in an 
oblong tuber. Both runners and stolons emit at the axils thready 
roots. 
The stems of H. prolifera, on the contrary, all creep beneath the 
soil. They occupy the sandy or muddy margins of streams and 
ponds, or other wet places. From the nodes arise solitary short 
petioles, supporting a peltate blade. The plant is very floriferous, 
nearly every axil producing its umbel on a stem usually shorter 
than the petioles. The stolons themselves are slender whitish or- 
gans, the internodes seldom more than half an inch long, and the 
nodes sending out abundant capillary roots. If these are removed 
from a growing plant the node is seen to consist of a narrow annu- 
lar enlargement, not exceeding one-quarter the diameter of the 
stem. So long as the plant continues to vegetate this condition is 
maintained, and no further nodular enlargement ensues. In this. 
climate, according to my observations, if the ground remains suffi- 
ciently wet it never occurs, 
the plant continuing to grow through- 
“Bull. Torr. Club, xiii, 28, 
tProc. U.S, Nat. Mus., xi, 455. 
tRev. Umb., 134. Manual Western Texas, 149. 
