1914] MANEVAL—MAGNOLIACEAE 4 
mosomes. Neither STRASBURGER (29) nor ANDREWS (1) deter- 
mined the exact number of chromosomes in the forms studied by 
them. 
The mature pollen grains are oval in shape, with rather thick 
walls. In the case of Magnolia they are binucleate (fig. 21), while 
those of Liriodendron are two-celled (fig. 4). This condition is 
found in the anthers before dehiscence occurs, which, in the latter 
species, is between May 15 and 18, and in the former about May 30. 
In early stages of development it is evident that the tapetum 
arises from the sporogenous tissue (fig. 15), later differing from it 
especially in size of cells and nuclei (fig. 17). Still later, when 
tetrads are forming, the tapetum consists of 2 or 3 layers of large, 
binucleate cells lining the walls of the loculi (fig. 1). Finally, as 
the pollen grains mature, the tapetum gradually disappears, but 
there is no evidence of migration of its nuclei among the develop- 
ing pollen grains (fig. 18). The walls of the loculi consist of 3 or 4 
layers of cells. As the anthers mature, the subepidermal layer of 
cells becomes differentiated into the usual type of cells which are 
active in dehiscence. 
The ovules in both Magnolia and Liriodendron are marginal in 
origin and anatropous, but there is considerable difference in the 
time of initiation of these organs. It occurs in the former as early 
as the first two weeks in December or earlier, while in the latter 
not until after the middle of March. Early in April, however, the ~ 
condition attained is about the same in both, and the two develop 
at the same rate until the completion of the embryo sac. The first 
rudiment of the inner integument appears when the megaspore 
mother cell is well differentiated (April 20), and soon afterward 
the outer integument is initiated (fig. 5). From the archesporial 
cell (fig. 22) a tapetal cell is cut off (fig. 23), apparently in both 
species, and the mother cell soon becomes deeply buried within the 
nucellus (fig. 24). By two successive divisions of the megaspore 
mother cell 4 megaspores are formed (figs. 6, 7, 25, 26, 27), the 
innermost of these in each case being functional, while the others 
degenerate. By the time the 4 megaspores have developed the 
innermost one comes to lie very deep within the nucellus (fig. 7). 
_ The development of’ the embryo sac is normal throughout. 
