A CONTRIBUTION TO THE LIFE HISTORY OF THE 
PONTEDERIACE#.* 
.WILSON R, SMITH. TW 
(WITH PLATES XIX—XX) 
Tue following investigation of Pontederia cordata was begun 
in the winter of 1897 as supplemental to a course in the special 
morphology of monocotyledons, unde¢ the direction of Dr. John 
M. Coulter. In the following summer, for purposes of compati- 
son, I collected and studied material of Zichhornia crassipes. 
This is, so far as I know, the first examination of the gameto- 
phyte generation of any of the Pontederiacee. While ie 
results, as might be expected, do not show any wide deviation 
from the usual series of events in monocotyledons, they have @ 
value as indicating the extent of variation within a given order, 
and, in the case of Eichhornia, within a given species. 
I wish here to acknowledge my indebtedness to Dr. C 
for criticisms and valuable suggestions: 
oulter 
EICHHORNIA CRASSIPES. 
MICROSPORES. 
: soungest 
fig. 30 represents a cross section of one of the young 
anthers I obtained. The tapetum is a distinct layer of small 
closely adherent to the spore mother cells, and often wedge . 
among them. Outside the tapetum are usually five 7 ee te 
wall cells, the innermost of which appears always to eeu 
before the tapetum gives any clear signs of collapse. [t's ne 
known that in their later stages the tapetal cells of anthers 
likely to become binucleate. Such a condition I have ne = 
found in a single case either in Eichhornia or in apes e 
the ripe anther there are, as usual, two layers sodas tO 
* Contributions from the Hull Botanical Laboratory. IX. [ma¥ 
324 
