562 Black : The imbedded antheridium in Dryopteris 



thallium, and it may remain so when mature {figure g). Figure 8 

 shows a form of antheridium occasionally met with. There is 

 here a slight projection above the surface of the prothallium. 

 This antheridium is peculiar in that it extends so deeply into the 

 prothallium. 



There seems to be no definite method for the further divisions 

 of the outer cell. In sections, two or more cells are seen in the 

 cover, irregular in size and depth. From this it will be seen that 

 there is no definite arrangement or number in the cells comprising 



the cover. In most cases the antheridium was situated under one 

 layer of cells, occasionally under two layers {^figure id). There 

 was a marked variety in the size of imbedded antheridia. All de- 

 grees of size and shape were found from those about as large as 

 the superficial type and rather globular to those more than twice 

 as large and very irregular in shape {^figures 7-p). The finding of 

 imbedded antheridia upon these prothallia was not an occasional 

 thing but a common occurrence, the majority of the prothallia 

 grown under the above-detailed conditions bearing one or more 

 imbedded antheridia. As a rule these were found upon the 

 largest prothallia, although occasionally one was seen on a smaller 

 prothallium. These deep-seated structures were always found to 

 be in the apical region or within a few cells of it- 

 Typical of cell divisions in normal antheridia, the cells in the 

 imbedded type divide simultaneously. The development of the 

 sperms in the imbedded antheridium was followed closely and was 

 found to differ in no way from that of the sperms in normal an- 

 theridia, a sperm from an imbedded organ appearing exactly like 

 a sperm from a superficial one. Owing to the occurrence of both 

 normal and imbedded antheridia on the same prothallium and the 

 similarity between the sperms, sperms from a deep-seated antheri- 



be 



/. 



of the apical region, in which are two imbedded antheridia and a 

 normal archegonium. More than one half of the antheridium, the 

 lower one in the figure, consists of sperm mother-cells, the rest of 

 the antheridium being made up of four large cells. These cells 

 have the granular cytoplasm characteristic of developing sex-cells. 

 Another case similar to the foregoing was observed {figure lo). 



