332 BOTANICAL GAZETTE {may 
PONTEDERIA CORDATA. 
Longitudinal sections of very young spikes furnished a com- 
plete series for the study of the organogeny of the flower. The 
order of succession of the floral organs is acropetal (fig. 42) and 
need not be dwelt upon. Both in stamens and carpels traces of 
zygomorphy are very early recognizable. 
The first indication of the ovule is a slight swelling on the 
inner wall of the lowermost carpel which is always the smallest 
(figs. 43, 432). Normally but one ovule makes its appearance. 
I had expected to find the beginnings of ovules in each of the 
three loculi, but the facts are otherwise; out of the hundreds of 
ovaries. sectioned I found but seven cases of a second ovule 
beginning, and no case of a second ovule reaching maturity. 
The various stages from the differentiation of an archesporial 
cell to the completion of the embryo sac can be followed easily 
in the plate (figs. 4¢-53). A few comments only will be neces- 
sary here. The dividing wall of the primary tapetal cell runs 
always, so far as I observed, in the same plane with reference to 
the axis of the flower. There is reason to believe that a 
often but three megaspore mother cells are formed. 3 
lengthening of the ovule is effected in part by an mare 
the epidermal and tapetal cells and the other cells of the ee 
apex (figs. 45-47, 48-52). Later, however, those cells i? the 
nucellus which have escaped destruction by the growth me 
megaspore divide transversely (cf figs. 48 and 53). The ae 
ing of the ovule is at first in a plane passing through the et = 
the flower. Afterwards the funiculus twists through oF us in 
ninety degrees so that the ovule comes to ie ee 
IE. 45. tral 
The embryo sac is very poor in protoplasm. . a a 
vacuole is formed and the cytoplasm is pushed = - markably 
very thin layer ( figs. 50-52). The egg apparatus 8 Ae defini- 
small and is crowded against the micropylar end. ded by the 
tive nucleus lies low down in the sac, and is oor ene (¢- 
strings of protoplasm trailed together by the polar 
