274 



Ox the Absence of Stomata ix Certain Ferxs. 



By W. H. Gilsert. 

 {Read March 23rd, 1877.) 



The group of Ferns referred to in this paper are those commonly 

 known as the filmy ferns, comprising the three genera — Hymeno- 

 phyllvm, Trichomanes, and Todt<: — a group containing forms, 

 perhaps the most delicate in appearance, structure, and constitution 

 of the whole family. 



These ferns are assumed to possess stomata in common with all 

 plants (save Fungi and Lichens) living under sub-aerial conditions, 

 at least I have found nothing to the contrary in any of the 

 authorities consulted, among which have heen most of the best and 

 latest ; in fact, the teaching of the English Text-hooks may be 

 summed up in this — "That all plants have stomata except such as 

 are wholly cellular, and those whose leaves- are wholly submerged :" 

 the first exception referring to Fungi and Lichens, the second to 

 those plants whose leaves are developed and always remain under 

 water, Saeh, however, goes a little further, and says, when speak- 

 ing of Mosses, " their leaves are composed of a single layer of 

 cells, and are, therefore, of necessity without stomata." He also, 

 in an earlier part of his work, when treating of the Hymenophyllacea, 

 states that the lamina of their fronds is composed of a single layer 

 of cells, making no remark however, concerning stomata, possibly 

 assuming that, as in S^laginella,vr\n\e absent for the same reason as 

 in Mosses from the lamina, they would be found along the midrib 

 and venation. 



In examining these ferns two methods have been employed — first, 

 by decoloring and staining to view them as transparent objects, and 

 thus, to make out their structure, so far as cell-walls and vessels are 

 concerned, undisturbed ; the other, by examining their surfaces, and 

 making sections of every part and in all directions while in a fresh 

 and natural condition. 



