UGULATE WOLTFIAS OF THE UNITED STATES. 103 
same time I should probably have taken the Florida plant 
for the type of the species inasmuch as it is constant with 
itself wherever you have found it ; and the Mexican plant 
would have been treated as a var. ahhreviata* " 
The habit of growth seems to vary according to the 
nature of its surroundings. In still water it collects in 
dense masses as intricately interwoven as the fibers of felt, 
while in flowing water it is more likely to be scattered — 
united only in small clusters which might aptly be termed 
families, since from the youngest up to the oldest plant each 
individual is attached by its stipe to the parent. These 
families take on a peculiar form. Each frond has a pro- 
nounced double curve — the curve edgewise of a saber and 
again curved sidewise as a part of a band. The young, 
growing from the pouch of the parent, continues in the 
direction of the band-like curvature of its parent 
so that at maturity the two form an almost regular 
semicircle. These each send out other young fronds 
which retain the curvature of their parents but are grow- 
ing edge to edge with them. This multiplication is 
continued until an almost complete hemisphere is 
produced t (pl- 64, f. 9). Directly at the upper pole 
this hemisphere is exposed to the air at the surface of the 
water, and at this point also, it will be readily seen, the 
base of each frond is situated. Thisgrouped formation{ fam- 
ilies ) seems to be adapted to catch any slight current arising 
from a disturbance of the water, for if the water is agitated 
these inverted basket-like bodies take on a rolling, rocking 
motion which sinks and carries them to a considerable dis- 
tance where again they come to the surface. This seems 
to be their mode of travel or dissemination — a sort of 
subaquatic tumble weed. From the curved form of the 
tips of the fronds it is easily seen how two or more 
* BuU. Torr. Bot. Club, vn. 65 (1880). 
t Looking from above, the curvature seems to be tmiformly downward 
aad to the right, thoagh I would hesitate to make such a statement definite 
