244 Mr. Valentine on the existence of Stomata in Mosses. 



existence ; and if my pencil will but do justice to my eye and my knife, I 

 feel confident of being able to produce a most interesting analysis. - 



I remain, my dear Sir, yours, very truly, 



Cae Bwld, near Carnarvon. WiLLIAM VALENTINE. 



March 1st, 1838. 



EXPLANATION OF TAB. XXI. 



Fig. 1. Longitudinal section of the theca of Orthotrichum diaphanum. 

 a. Operculum, b. Theca. c. Thecal membrane, d. Sporular 

 membrane, e. A stoma, the projecting cells of the cuticle being 

 open. f. A stoma, the projecting cells of cuticle having closed 

 over the stoma, g. Columella, h. Sporular cavity, i. Pedicel 

 of the columella, k. Apophysis. /. External peristome — the in- 

 ternal cannot be seen in section, m. Metula. 



Fig. 2. External view of a stoma from the same. The projecting cells are 

 nearly closed. 



Fig. 3. The same. The projecting cells are more open, and allow the true 

 stoma to be seen within. 



Fig. 4. Internal view of the same. 



Fig. 5. Transverse section of the same. The projecting cells are fully ex- 

 panded. 



Fig. 6. Stomata of Funaria hygrometrica — each composed of one cell in the 

 form of a hollow ring. 



Fig. 7- Longitudinal section of a young theca of the same plant, a. Oper- 

 culum, b. Annulus. c. Theca. d. Thecal membrane, e. Co- 

 lumella, f. Sporular membrane, g. Sporular sac. h. One of 

 the strings of elongated cells which connect the sporular mem- 

 brane with the thecal membrane ; — these only occur in such 

 mosses as have a space between the two membranes in their 



