10 HANDBOOK OF MOSSES. 



two membranes or coats, an inner and an outer one, in- 

 closing a thickened granular mass. Though similar in 

 function to the seeds of flowering plants, they differ from 

 those organs, in being capable of germinating from any part 

 of their surface, and in possessing no embryo (the young 

 plant contained in the seed) ; hence plants developed from 

 spores are termed Acotyledons (Gr. a, without, and kotu- 

 ledon, a seed-lobe). The spores which are formed in the 

 capsule are the bodies from which the moss-plant is nor- 

 mally developed. 



But many even of our common mosses rarely produce 

 their fruit, and are perpetuated in other ways; as, for 

 instance, by gemmae, which may be seen forming little 

 globular heads (2 c) on the top of a pale, naked stalk (2 b) in 

 Aulacomnion androgynum (2), so frequent on wayside banks; 

 or from thread-like cellular bodies, abundant on the leaves 

 of some mosses, Orthotrichum Lyellii, for instance, frequent 

 on poplars, elms, etc. ; or from bud-like bodies formed in 

 the axils of the leaves, as in Bryum annotinum, found on 

 sandy banks ; or even detached leaves may give origin to a 

 new plant, as in Campy lopus pyriformis, frequent on heath 

 lands. 



When the spores germinate, they give rise to a green, 

 thread-like body, called the protonema (fig. 3 b), which is 

 formed by the protrusion of the inner membrane of the 

 spore through the outer one. This, by frequent cell- 

 division, becomes elongated and branched. The primary 

 branch, at first green, frequently turns brown, and, in some 

 cases, penetrates the ground and performs the function of a 

 root. The secondary branches are well charged with chloro- 

 phyll (green, granular matter in the interior of the cell), and 

 branch frequently. On various parts of the protonema 

 bud-like bodies arise. These are the rudimentary moss- 

 plant. From the buds roots are sent down into the medium 

 on which they grow. By frequently repeated cell-division 

 these buds develop into the leafy moss-stem. Mosses, like 

 ferns, horsetails, etc., grow at the apex only, and are hence 

 termed Acrogens (plants which increase at the summit only). 



The protonema, which looks very like masses of green 



