﻿24S BOTANICAL GAZETTE [april 



gium, we should expect a general similarity in the protoplasmic 

 activities of each structure. There is the general agreement that 

 the protoplasm segments by cleavage planes determined chiefly 

 by vacuoles; but beyond this the activities of the two structures 

 have little in common and a great many peculiarities. 



As is well known, there is no mitosis in the sporangium. A 

 ^ large number of nuclei are carried into the tip of the hypha by 



the accumulation of protoplasm there. Vacuoles collect and 

 develop in the center of the young sporangium (y?^. J(5)t and 

 flowing together form a large central space inclosed in a vacuo- 

 lar membrane {fig> 31)' The nuclei then lie scattered in the 

 peripheral layer of protoplasm, and presently clefts appear 

 which work outward between the nuclei from the central 

 vacuole {fig- 32). The clefts divide the protoplasm so that it 

 is cut up into polygonal areas, with clearer regions between. 

 These are the zoospore origins, and each contains a nucleus. 



Rothert's explanations of succeeding conditions, which have ^ 



^ 



also been confirmed by Humphrey and Hartog, seem entirely 

 satisfactory. The sporangium is in a state of turgor when the 

 clefts arise and push their way from the central vacuole toward 

 the periphery. They finally reach the cell wall and immedi- 

 ately make possible the relief of the fluid in the central vacuole. 

 There is at once a very evident decrease in turgor, which has an 

 interesting effect on the appearance of the spore origins. The 

 polygonal areas run together, and the whole sporangium 

 becomes again almost homogeneous in structure. This means 

 that the contraction of the sporangium brings the spore origins 

 so close together that the clefts become almost obliterated. 

 The spore origins also swell. They then begin to separate 

 slowly, preliminary to their being finally rounded off as zoospores. 

 There is a period when the small masses of protoplasm form a 

 very irregular network through the sporangium {fig'33)f^^^ 

 this is followed by a more regular arrangement {fig- 34)^ ^^ 

 which the spore origins are connected by ver\^ delicate proto- 

 plasmic strands. The latter are finally broken and the bodies 

 round off as zoospores. 



The writer searched persistently in the sporangium for cyto- 



