June, 1905.] Embryo Sac and Embryo of Batrachium. 
355 
The primary sporogenous cells continue to divide and appar- 
ently give rise to the axial layer of tapetal cells. The origin of 
the peripheral layer from the wall cells and the axial layer from 
the sporogenous, seems to accord with their origin in R. delphi- 
nifolius, both from examination of the slides and from the 
observations recorded in Coulter’s Life History of Ranunculus 
(3). This refers the origin of the tapetum to the primary arche- 
sporium instead of referring the axial layer to the inner tissue of 
the androecium. Frequently a splitting was observed between 
the sterile wall layers and the tapetum but quite as often it could 
be seen between the tapetum and the sporogenous tissue (Fig. 9), 
and sometimes seemed separated from both. As the stamen 
matures the cells are forced past each other and misplaced, 
making it extremely difficult to determine the origin of the 
tapetum unless a careful study of a series of stages has been made. 
The primary sporogenous cells then divide a number of times 
so that a central cross section shows sometimes as many as 
twelve microsporocytes (Fig. 8), while a longitudinal section 
shows from three to four rows (Fig. 11). The tapetal layer does 
not disintegrate early but is still quite well organized after the 
separation of the tetrads. 
The microsporocyte divides to form four microspores (Fig. 
12-13). No cases of more were found as has been reported in 
Ficaria (4) and other Ranunculaceae but in some cases the sep- 
aration is incomplete. This is shown in one of the pollen grains 
in Fig. 25. In many cases the microspore never germinates (Fig. 
14), in fact scarcely one to four. The tube nucleus and the gen- 
erative nucleus lie close together. Just before pollination the 
generative cell becomes lenticular and divides to form the sperm 
nuclei (Fig. 15). These are not readily seen because of the 
abundant starch granules, the deep color which the pollen grain 
takes, and the crowding of the three nuclei. In the slides of R. 
delphinifolius there were found similar cases of two male nuclei 
before the germination of the pollen tube. 
Before the lamina has entirely enclosed the nucellus, the 
archesporium can be distinguished (Fig. 16-17). The occurrence 
of two or more archesporial cells is not at all unusual and in manv 
cases the struggle for supremacy results disastrously for all con- 
cerned. The remains of other archesporial cells can almost always 
be seen around the megasporocyte. There is no evidence of the cut- 
ting off of any primary parietal cell but the reduction division 
occurs at once. The low^er of the two cells divides first and in 
many cases the division of the upper seemed never to pass beyond 
the formation of the spindle (Fig. 18-19). This is not unlike the 
development of the megaspores as reported by Mottier (S). In 
a few cases there seemed to be two complete sets of megaspores 
but the writer did not observe any twin embryo sacs though it is 
