446 BOTANICAL GAZETTE [December 



sporangium 



me 



inferred that only one sporangium had appeared. Referring to 



Strasburger sugg 



more 



rangia should have appeared simultaneously; and that later those about 

 the base of the large central sporangium should have aborted. In 



4 



the microsporocarp he found microsporangia, in numbers as high as 

 forty, arising £rom a short ^^ columella." He further said that he 

 found no sign of the club-shaped ending of the columella which 

 Meyen had described earlier. 



In 1889 Strasburger (3) reinvestigated the subject. According 



female 



macrosporan 



a ^^^^^^o-*-r^'' 



gmm" at the apex of the columella. In the ^^macrosporocarp 

 this went on developing, but in the microsporocarp its growth was soon 

 inhibited, while from the columella ^ beneath it microsporangial 

 primordia were constantly arising. He suggested that the develop- 

 ment of one or the other might depend upon the method of nutrition. 

 In 1893 Campbell (4), referring to Azolla filiculoideSy wrote: 



For some time each sporocarp rudiment grows by a three-sided apical cell. 



Next a slight OlltPmwth k nh<iprvf^r] npi^r fTip Kqca nf flip vnnnor cnril.*?. whlch formS 



a ring-shaped projection; 



point 



is the beginning of the indusium or sporocarp 

 two sorts of sori differ. In the macrosporic one, 

 body of a single sjKDrangium; in the microsporic 



it forms a columella, from which latter the microsporangia appear 

 outgrowths. 



speakmg of the megasporocarp 



When the sporangium is about half 



sporangia 



they show divisions which recall the earlier ones in the macrosporangium. Their 

 position corresponds to that of the microsporangia, so that although formed much 

 later than the macrosporangium, it is pretty safe to assume that Azolla is derived 

 from some form in which, as in Salvinia, there are several macrosporangia in the 



sporocarp. .... In the male sorus, as we have already seen, the apical cell of. the 

 young rudiment does not form a sporangium, but gives rise to a central columella 

 or placenta from which microsporangia arise laterally, while the end projects 

 as a cylindrical body. This latter was observed by Meyen, but Strasburger 

 seems for some reason to have overlooked it. I found it in all of my sections of 

 the male sorus. 



