Lewis —The Life History of Griffithsia Borneticina, 66 1 
peripheral cells. The result of the fusion is the production of a very large, 
irregularly shaped placenta, on the upper surface of which the sporogenous 
lobes are formed (Figs. 85, 87). 
The placenta contains nuclei from three sources: (1) the original 
nuclei of the peripheral and auxiliary cells, which appear to take no part in 
spore formation ; (2) the numerous nuclei of the central cell, which lie in 
the base of the placenta, a region from which no sporogenous lobes are 
formed ; and (3) the numerous nuclei resulting from the division of the 
fusion nucleus. These last lie in the upper region of the placenta, where 
the sporogenous lobes are being formed, and appear to be the only nuclei 
to enter these. A similar placenta, with numerous nuclei of diverse origin, 
has been described in Chylocladia , by Hassencamp ( 40 ). 
At least in some cases, the nuclei from the central cell appear to 
become abnormal and break down. The chromatin forms a crescent-shaped 
mass applied to the nuclear membrane on one side (Fig. 88), the nuclei 
swell, their outlines become faint, and finally their contents mingle with the 
cytoplasm. Not all of the nuclei from the central cell degenerate, and 
it is often difficult to distinguish those which remain normal from the 
sporogenous nuclei, especially in the older cystocarps, except by their 
position in the cell. 
The mode of division of the sporogenous lobes seems to vary consider- 
ably in different lobes. The series of figures from 89-93 (F 1 - LI and LII) 
gives a fair idea of what usually takes place. Following the division of the 
nucleus of one of the protuberances mentioned as being formed on the free 
surface of the placental cell or on the upper part of the placenta, small curved 
segments are cut off from the outer surfaces of the protuberance in much 
the same way as a segment is cut off from the apical vegetative cell, with 
this difference, however, that the cells of the sporogenous lobes are usually 
uninucleate. In this way a compact tissue is formed, the cells of which 
round themselves off, each cell producing a carpospore. As the cells round 
off, the sporogenous lobe becomes converted into branched chains of oval 
cells. The links of a chain are free at the sides, but connected with each 
other above and below by a narrow strand of cytoplasm ; midway between 
connected spores occur callus-like plugs similar to those lying in the pits 
between adjacent vegetative cells. From the time when they first round 
off, the spores increase greatly in size. When the spores are ready to be 
shed, their diameter is about 30-35 /x, their length 40-54 fj., the diameter of 
the nuclei 8*5- 9 j u. 
This is the usual history of a sporogenous lobe. In some cases a 
difference is presented because of the fact that the spore-mother-cells are 
rounded off at a very early age, so that the sporogenous lobe is not a 
compact tissue when young, but a group of rounded cells (Figs. 94, 95). 
There is some evidence that in this case the method of cell-division in the 
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