6 



The Naturalist. 



consists of a double layer of cells before fertilization, and the neck 

 consists of a single layer of cells of from four to six rows. They 

 enclose together an axial row of cells, the lowest of which produces 

 the oosphere from its protoplasm by rujuvenescence (that is — the form- 

 ation of a cell from the whole of a protoplasm of an already existing cell) 

 while the rest of the axial cells become mucilaginous prior to the 

 fertilization of the oosphere, this mucilage bursts the four apical cells 

 and allows the antherozoids access to the oosphere. From the fertilized 

 oosphere is produced the sporogonium, which in Sphagnum develops 

 almost perfectly within the growing ventral portion of the archego- 

 nium, which is transformed into the calyptra. Tn all other mosses 

 the calyptra is torn away at its base by the elongation of the sporo- 

 gonium, usually long before the spore capsule is developed, and is 

 raised up as a cap, except in ArcJiidium and its allies. The wall of 

 the capsule consists of several layers of cells having a distinct 

 epidermis, sometimes with stomata. In the development of the sporo- 

 gonium the oosphere is clothed with a cell wall, and divides by a 

 slightly inclined wall ; division continues both vertically and trans- 

 versely, and a multicellular body results. The mother-cells of the 

 spores become isolated, and divide into four in all parts of the capsule 

 at once. The length of time required for the perfect develoj)ment of 

 the fmit varies from three to twelve months. 



Mosses are divided naturally into four families : Sphagnacea^ 

 having one genus ; Andreceacece, having a few genera ; Phasmcece, 

 having a few genera ; and Bi^yacecB (the true moss), all the remaining 

 genera. 



The spores of the Sphagnacece in water produce a branched protonema, 

 but on a solid substratum a flat pro-embryo, while the abundant 

 protonema of the BryacecB is wanting, and they only produce rhizoids 

 when young. The antheridia stand by the side of the leaves, and are 

 never terminal, and have a roundish form and a long pedicel. The 

 archegonia are at the blunt end of the female branch, and are like 

 those of the mosses. The summit of the branch begins to develop 

 after the formation of the sporogonium, and elevates the latter 

 enclosed in the calyptra ; this stalk is called a pseudopodium, and of 

 course is quite different from a seta. The calyptra is ruptured 

 irregularly, and the theca opens by detaching the upper part as 

 a lid. 



The Audreceaceoe are small, very leafy and much branched mosses, 

 gr-jwing in a caespitose manner ; their long apiculate theca is sup- 



