LIGDLATE WOLFFIAS OF THE UNITED STATES. 107 
younger fronds in all stages of development are to be seen 
in the pouches of both of these, wholly included within 
them. Again I have failed to find an instance where two 
fully grown fronds were coimected — the offspring com- 
pleting its growth after being 8et free and .scarcely 
mature when it in turn casts its offspring. How many 
individuals one parent frond may give rise to I am unable 
to state, though I have observed as many as four in their 
various stages of development, all attached to the same 
matrix, which probably continues to successively develop 
more. 
As before stated, the frond grows in a band-like curve, 
but instead of being flat as in gladiata it has the lateral 
margins at maturity upturned like the sides of a boat 
(pi. 65, f. 6). In these, too, the shape seems to 
be adapted for catching water currents and thereby 
being carried to distant points. When the water is 
disturbed the plants dive in all directions from the 
surface, and from their peculiar form assume a 
somersault or rotary motion — the direction of least resist- 
ance for their shape — then slowly rise to the surface 
again.* This power to float is due to the abundance of 
large chambers in the tissue of the basal portion of the 
fronds, filled with some gas (pi. 65, f . 5 ). 
Wolffia lingulata was named and described by Dr. 
Friedrich Hegelmaier,t from material collected in Mexico 
by Louis Hahn in 1868. The plant is a thin frond, tongue- 
shaped and entire, with a rounded apex and a slightly 
oblique truncated base, which is split horizontally to form 
a triangular pouch, in the basal angle of which the budding 
of reproduction takes place (pi. 65, 1-5). This basal 
much resembling a sand-flea. It swims to the surface and there attaches 
itself to the under surface of a frond, 
