Holloway. — The Pro! hull us and Young Plant of Tmesipteris. 



15 



Development of the Sexual Organs. 



As has been stated in the preceding section, developing antheridia were 

 commonly seen at the growing apices of the prothalli, but only in a very 

 few prothalli did I find groups of young archegonia. In the older regions 

 of the prothallus, where both antheridia and archegonia not infrequently 

 arise singly amongst old organs, I did not find any in the earliest stages 

 of development, though many of both kinds in later stages were to be 

 seen. The fact that the apex of the prothallus is generally very broad 

 militated somewhat against the study of the young developing organs, 

 for transverse sections in this curving region of the prothallus-head cut 



ar. 



Fig. 17. — Transverse section of main limb of prothallus in older region, showing 

 portions of old sexual organs, also two fertilized archegonia. X 100. 



them often obliquely. However, I was able to obtain a fairly good series 

 of both, although certain points must be left for a more complete study. 

 Perhaps it would not be out of place for me to describe at this juncture 

 the methods adopted for the preparation of my material for microscopic 

 investigation. After the preliminary study and drawing of each prothallus 

 as it was dissected out of the tree-fern humus, it was killed and fixed by 

 immersing for twenty-four hours in a solution of chromo-acetic acid, the 

 formula for which is that given by Chamberlain on p. 21 of his Methods 

 in Plant Histology (3rd ed., 1915). This was found to answer quite satis- 

 factorily so far as the more obvious histology of the prothalli and sexual 



