ASPIDIUM SPOROPHYTE 309 



cells similar to the above : there are stomata with two 

 guard-cells. 



The development of these stomata may be studied with ad- 

 vantage in young leaves, by stripping off the epidermis, or by 

 cutting tangential sections. Special attention may be given to 

 the peculiar case of Aneimia, in which the mother-cell of a stoma 

 is cut off from an epidermal cell by a cylindrical wall, as a circular 

 hole is cut in a sheet of wadding by a wad-punch. 



The Sporangia. 



XVIII. Cut transverse sections through pinnae of 

 leaves which bear sori, taking care that the sections 

 shall pass through one or more sori : mount as before, 

 and examine with a low power. Note 



1. The structure of the pinna, as above described. 



2. Opposite to, and seated upon a rib will be found 

 the membranous indusium, which, like an umbrella, 

 covers over 



3. The sporangia, which are biconvex-lens-shaped, 

 brown, stalked capsules, attached to the rib, and filled 

 with 



4. Numerous roundish, brown, unicellular spores. 

 Observe more closely the structure of the single 



sporangium. It is composed of 



i. The stalk, which is of considerable length, and 

 usually consists of three rows of cells. 



Stalked glandular bodies are often found as lateral branches on 

 the stalk of the sporangium in this species. 



ii. The capsule, which has the form of a biconvex 

 lens, and consists of a marginal series of cells with 



