1899] DEVELOPMENT OF THE MICROSPORANGIUM 343 
The division of the generative nucleus into the two sperm 
wclei must take place in the pollen tube, good stages of which 
were not obtained. Except in the one point above mentioned, 
| the microspores of Convallaria do not differ in any essential way 
ftom those described by Strasburger”® for a large number of the 
higher monocotyledons. . 
POTAMOGETON FOLIOSUS RAF. 
The numerous investigations recently made upon plants 
belonging to the orders Alismacee and Naidacee have shown 
that many peculiar conditions are to be found among these 
soups of monocotyledons. During the past summer the writer 
Was able to procure excellent material of Potamogeton foliosus in 
the ponds about Ithaca - and it was decided to make a detailed 
Study of this plant for comparison with the studies already made 
‘Yothers. No one seems to have investigated this genus from 
| ‘cytological standpoint. 
f the papers on nearly related plants must be mentioned 
. that on Naias by Magnus,?7 on Naias and Zannichellia by Camp- 
ll® and on Alisma” and Sagittaria° by Schaffner. 
S The material was collected during the months of July and 
August, at which time the oldest flowers are just producing fruit. 
The floral Spikes mature in succession as the plant branches, so 
by the very youngest flowers and also the fruits may be found 
‘nthe same individual. There being no cutinized layer sur- 
utding the bud, the latter is especially easy to penetrate with 
mg agent. The material used for this study was therefore 
the “eptionally good condition. As in the case of Convallaria, 
“collections Were made at certain times during the day and 
the result also was exactly the same. 
: age tttssvorginge bei den Phanerugamen 22. 1884. 
= Fage zur Kenntniss der Gattung Naias. Berlin. 1870. 
A 
yy, P'sical study of Naias and Zannichellia. Proc. Calif. Acad. Sci. 11. 
“The emb 
% 
TY sac of Alisma plantago. Bot. GAZ. 21:123. 1896. 
‘ontibution to the life history of Sagittaria variabilts. Bot. GaZ. 23252+ 
