244 BOTANICAL GAZETTE [APRIL 
other regions become more active in division and more deepiy 
stainable. The former may be called the sterile regions, since 
they form the walls, trabeculz, and tapetum, and the latter the 
fertile region, since they give rise to the spores. Even in 
unstained sections the difference is noticeable as one of relative 
abundance of protoplasmic contents. 
At first it is difficult to see clearly the limits of the regions 
or to make out their arrangement. But in older sporangia they 
are seen to be disposed in irregular bands extending from the 
base of the sporangium outwards to the wall. The published 
drawings, and unfortunately in some cases the written descrip- 
tion also, are calculated to convey an erroneous idea of the 
trabecule. They are not partitions, but, though irregular in 
outline and frequently branched and anastomosed, are com- 
parable rather to pillars. It is accordingly incorrect to speak 
of the sporangium as chambered, for the fertile cells are not 
segregated into loculi, but form a continuous mass pierced here 
and there by the trabecule. It is hoped that figs. 44-47 will 
make the relations of the trabeculae clear. The shaded por- 
tions of these drawings represent the fertile regions, and the 
unshaded portions the trabeculze and walls. The continuity of 
the sporogenous mass is clearly seen in the tangential section 
(fig. 46). 
A more detailed account of the development of the micro- 
sporangium will now be given. Fig. 8 shows a small portion 
of a microsporangium in which the differentiation into sterile 
and fertile regions has just begun. The fertile cells stain deeply 
and are still rapidly multiplying, as is evidenced by the many 
karyokinetic figures. The sterile cells have almost entirely 
ceased divisions, though here and there a dividing cell may be 
found. It is important to notice that the one character in which 
the two regions differ is in the relative abundance of protoplasm, 
the fertile cells being densely filled with deeply staining cyto 
plasm, while the cytoplasm of the sterile cells is beautifully 
vacuolated. In all other respects the cells of the two regions 
are essentially alike. They are not markedly different in s!Z@ 
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~ bolpagye cowl baleen ae 
