1894.] fistology of the Pontederiacee. 179 
water and spreading over the surface by means of off-shoots. 
It has a thick root-stock, and long roots with very many lat- 
eral rootlets, so that a light feathery appearance is given to 
the whole. The roots are colored a dark violet-blue.  F. Hil- 
debrand suggests that the probable biological reason for this 
is to provide immunity from living animals in the water by 
bulb, which serves to float the plant. The flowers of P. cras- 
“IPes, as well as of P. cordata L., are violet blue and ephem- 
eral. P. cordata, also, has a thick root-stock. It produces 
erect long-petioled mostly heart-shaped leaves, and a stem 
with a single leaf bearing the spike of flowers. # 
he three Species of Heteranthera, H. reniformis Ruiz & 
Vy 4. limosa Vahl., and H. graminea Vahl. are ‘‘creep- 
we: Hoating, or submerged low herbs, in mud or shallow 
water, with a 1-few-flowered spathe bursting from the sheath- 
ing side or base of a petiole.” 
eel a sectioning were hardened 24-48 hours in a 
Gree att apparatus and afterward imbedded in collodion. 
Mia was experienced in infiltrating thoroughly with 
ary ton the parts of P. crassipes above the water, the stem, 
$0 ak Presumably on account of the floating tissues being 
“+ samsaa to liquids, Especially was this difficulty found 
ized “very part of the leaf tissues, parts of which were cutin- 
difficult € loose aerating tissues of the root present no such 
‘Ost Saece - any of the tissues of_the other rae 
brought oat. ing points in the histology of this order we 
The ape Oe P Crassipes presents a beautiful structure. 
ap IS very large and is organically connected with the 
ie ‘only, being free at its upper end (fig. 3)- Good- 
Ponteder: that this sort of a cap occurs in several species of 
centimeter and envelops the root for the length of half a 
P . > 
n Sfor 2.5™ or even more. A median longi- 
3S well a Toot-tip shows well the connection of the cap 
“S the structure of the tip itself. Haematoxylin 
