CHAPTER X 



THE HOMOSPOROUS LEPTOSPORANGIAT^ (FILICES) 



Fam. I. Osmundace;e (Diels (/)) 



The Osmundacese, which in many respects form a transition 

 from the eusporangiate to the leptosporangiate Filicinese, are 

 represented by two genera, Todea (inc. Leptopteris) , with four 

 species, mostly confined to Australasia, one species only 

 being found in South Africa; Osmunda, with six or seven 

 species, belonging mainly to the temperate and warm temper- 

 ate regions of the northern hemisphere. The widely distrib- 

 uted species O. regalis is found also in South Africa, but other- 

 wise they belong exclusively to the northern hemisphere. Os- 

 munda has the large sporangia borne on very much modified 

 sporophylls, which recall strongly those of Botrychium or Hel- 

 minthostachys ; Todea, while its sporangia are like those of 

 Osmunda, has them borne upon the backs of ordinary leaves. 



The Gametophyte 



The development of the gametophyte is completely known 

 in Osmunda (Kny (5); Campbell (12)) and somewhat less 

 perfectly in Todea (Luerssen (3)), which does not, however, 

 seem to differ essentially from Osmunda. In the latter there 

 is considerable difference in the species examined. In all of 

 them the spores contain chlorophyll at maturity, and quickly 

 lose their power of germination. Sown as soon as ripe, they 

 germinate very promptly, and the first division of the spore 

 often takes place within twenty-four hours. The early stages 

 show great variation, even in the same species, and these seem 

 to be often quite independent of external conditions. The un- 



346 



