580 FILICALES 



of the sporangium to the receptacle, and that the distal part of the annulus 

 is directed obliquely towards its apex. This being the case for all the 

 sporangia, the free action of the annulus on dehiscence is assured for each 

 individual sporangium; this may be compared with No. 95 of Hym. dilatatum. 

 The stomium in Tr. radicans is of very simple construction : in the last of 

 the drawings it is shown in surface view, with the slit of dehiscence gaping 

 between the two cells. Comparing this with No. 96 of Hym. dilatatum, we 



see again that Trichomanes 



^~~~~^ is constructed on the same 



general plan, of which it ap- 

 pears as a simplified edition. 

 The origin of the spor- 

 angium has been followed 

 by Prantl 1 in Trichomanes 

 ^\\ speciosum, with which that 



of Hymenophyllum agrees in 

 essentials. The parent cell 

 has a square base, and grows 

 out into a papilla, with seg- 

 mentation according to the 

 usual Leptosporangiate type; 

 but it is important to notice 

 that the first segmentation 

 strikes the basal wall of the 

 parent cell (Fig. 326), a con- 

 FIG. 326. dition which is seen in the 



Trichomanes speciosum, Willd. (=7\ radicans), transverse massive Sporangia of the 

 section of the receptacle, showing early segmentation of the Ci mri i:~~ c nfh^r rhan in fVi^ 

 sporangia. (After Prantl.) 



more advanced Ferns. 



The comparison thus suggested with the Fern-types which have large 

 sporangia is borne out by the facts which follow from enumeration of the 

 spores produced. The Hymenophyllaceae show among their species a wider 

 range of number of spores per sporangium than has been noted for any 

 other family of Ferns : while certain of their species approach, or even equal 

 the high numbers of the Gleicheniaceae, Schizaeaceae, and Osmundaceae, 

 in others the number is distinctly low : it will be seen that the species of 

 Hymenophyllum give for the most part a higher output per sporangium than 

 Trichomanes.^ The typical number for H. Tunbridgense was found to be 

 256-512, and for H. sericeum 256, while that of H. dilatatum and IVilsoni 

 was 128; but for six species of Trichomanes examined the typical numbers 

 varied from 32 to 64. Trichomanes reniforme, however, which is in many 

 respects an isolated and peculiar species, has the typical number of 256, 

 thus corresponding to Hymenophyllum rather than to its own genus. 



Seeing that in Trichomanes the usual output per sporangium is lower 



} Hymenophyllaceen, p. 38. 2 For full details see Studies, iv. , p. 64. 



