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448 BOTANICAL GAZETTE [December 



and a single layer of tapetal cells surrounding a mass of eight mega- 

 spore mother cells in synapsis. There is no trace of an annulus of 

 any sort to be found either at this or any later stage. By this time 

 the sporocarp wall has usually grown up so as almost to inclose the 

 sporangium, while the stalk of the sporangium is likely to be at least 



(fig. 4), .While the moth 



synapsis 



Iter cells of the sporangium stalk enlarge so as to 

 (/^^- 5)' These enlarged cells have nuclei larger 



becomes 



{h 



mc). 



microsporan 



carp. Shortly after the microsporangia appear, the walls of the 



tapetum 



mass of cytoplasm. Surrounded by this tapetal cytoplasm 

 :i, the megaspore mother cells have now separated from each 



(fig 



megasporangmm 



this point. When this occurs the megaspore mother cells become 

 shrunken, the tapetal nuclei appear small and more densely granular 

 than in the healthy sporangia, and the cytoplasm takes on a coarse, 

 loosely granular appearance. As this breaking down goes on in the 

 raegasporangium, more and more microsporangial primordia appear 

 at its base. This, however, is not the usual course of events. Ordi- 

 narily the growth of the megasporangium is not inhibited until after 

 it has passed the spore mother-cell stage. 



In almost every case, the megasporangium continues its growth in 

 size while the young microsporangia are developing at its base. 



mother cells divide simultaneously (fig- 7) 

 to produce the eight tetrads {fig. 8) . Even while this division of the 

 megaspore mother cells is taking place, growth in the microsporangia 

 continues, as is readily seen by the fact that cell division sometimes 

 takes place there {fig. 7, mc). It is therefore after the formation of 



the megaspore tetrads {fig. 8) that the critical st; 

 ment is reached. 



megaspore 



o 



At this stage the sporocarp wall, which consists of only two layers 

 of cells, has grown up beyond the apex of the megasporangium and 



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