THE SPORANGIA OF THISMIA AMERICANA 
NorMA E,. PFEIFFER 
(WITH PLATE XVI) 
Of the investigations among Burmanniaceae, the morphologi- 
cal studies of TreuB, Jonow, and Ernst and BERNARD are 
prominent. These studies included both chlorophyllous and de- 
pendent forms, although the latter are better represented. The 
accounts vary considerably in completeness, since in the earlier 
ones close stages are sometimes lacking. 
That there is variety within the family in development up to 
the mature seed is evidenced in the widely different accounts for 
those forms in which there is no evidence of fertilization, as com- 
pared with those where this process undoubtedly occurs. The net 
product seems to be approximately the same, that is, a small mass 
of endosperm cells about an embryo of from 2-10 or more cells, 
usually with no differentiation. A striking exception occurs in 
Thismia clandestina, which has a 3-celled suspensor and a spherical 
body differentiated into 2 layers. As in Orchidaceae (12), how- 
ever, the preliminaries to this vary. Division of the megaspore 
mother cell may produce a row of 2 cells (as Burmannia candida, 5), 
in which the inner cell gives rise to the embryo sac; or a row of 3 
cells, the innermost of which, a true megaspore, functions in pro- 
ducing the female gametophyte; or the usual tetrad of angiosperms, 
of which the innermost megaspore is functional. a 
In the production of these cells the mother cell may go through 
a reduction division (as Burmannia Championii, 5), in which case 
fertilization is the rule; or it may divide by an ordinary mitotic 
division, so that the progeny have the double number of chromo- 
somes rather than the reduced number (Burmannia coelestis, 2). 
In all cases the embryo sac mother cell, whether a megaspore 
or the result of a single division. of the archesporial cell, develops 
by 3 consecutive divisions to produce the 8-celled stage. Polarity 
is early evident, and the egg apparatus is organized, with small 
Botanical Gazette, vol. 66] [354 
