396 



BOTANICAL GAZETTE 



[NOVEMBER 



drawn from a specimen with sporangia like those in fig. g, B and C, 

 and in this respect is characteristic. 



Sections of sporangia, like those shown in fig. g, B and C, 

 show that the smaller sporangia contain no spores at all (fig. 10). 

 In most of these cases the sporangium wall is from 4 to 6 cells 

 thick, with the inner layer not differentiated into a definite tapetum, 

 and the outer lacking the anticlinal thickenings so characteristic 

 of sporangia which produce even imperfect spores (fig. 11). In 

 extreme cases the sporangium is a mere mass of parenchyma cells; 

 in others, a narrow streak of mucilage indicates that sporogenous 

 tissue had begun to form; in still others, like the one shown in 



I 





n 







A B CD 



Fig. 9. — A,B, C,B.dissectum; D, B. obliquum; X2 



fig. 10, a considerable mass of sporogenous tissue has been formed; 

 and in a few cases it could be seen tha£ the mucilaginous mass 

 consisted partly of imperfect, disorganizing spores. 



In the apparently perfect sporangia of B. dissectum many 

 of the spores are somewhat smaller than the average size for 

 B. obliquum, and there are many spores which look as if they might 

 be abortive. Fig. n shows six spores still floating in the tapetal 

 Plasmodium. The two spores at the upper left, one of them 

 triangular in outline, are doubtless abortive; of the other four, 

 only the one at the lower left has the full diameter of a normal 

 spore of B. obliquum. The epidermal layer has anticlinal thicken- 

 ings, as in normal sporangia, which dehisce and shed their spores. 



