352 BOTANY. 



but in others (Funaria, Mnium, Bryum, etc.) there is an 

 axial bundle of very narrow thin-walled-cells ; in still others 

 (Atrichum, Polytriehwn, etc.) the cells of the central bundle 

 are considerably thickened, and in the last-named genus 

 there are extra-axial bundles. In a few cases there have 

 been observed bundles of thin-walled cells extending from 

 the leaves obliquely through the tissues of the stem to the 

 central bundle. From the foregoing statements it cannot 

 be doubted that the Mosses possess rudimentary fibro-vascu- 

 lar bundles. Stomata resembling those of the higher plants 

 occur on the capsules ; they are not found upon the leaves 

 or stems. The stem always grows from an apical cell. 



450. Mosses are, for the most part, aerial plants, growing 

 upon moist earth or rocks, or even upon the sides of trees, 

 a comparatively small number of species being aquatic ; they 

 range in size from less than a millimetre to many centimetres 

 in length, the most common height being from two to four 

 centimetres. They are all chlorophyll-bearing plants, and are 

 generally of a bright green color ; occasionally, however, they 

 are whitish or brownish. 



460. The sexual organs of Mosses consist of antheridia 

 and archegonia ; they are usually found upon the end of the 

 leafy axis, and generally occur in considerable numbers. 

 Most of the species are either monoecious or dioecious, while 

 some are hermaphrodite. There is, however, but little value 

 to be attached to the kind of inflorescence, as it is often dif- 

 ferent in genera which are certainly near allies. Even in 

 the same genus some of the species may be dioecious, while 

 others are monoecious or hermaphrodite ; and occasionally, as 

 in the genus Bryum, the three kinds of inflorescence are 

 found ; rarely a species is itself variable in this respect 

 e.g., Bryum crudum, which is mostly hermaphrodite, but 

 sometimes dioecious. 



461. The antheridia are generally club-shaped, stalked 

 bodies (spherical in Sphagnacece), with a wall composed of a 

 single layer of cells enclosing a mass of sperm-cells, each of 

 which contains a bi-ciliate, spirally coiled, thread-shaped sper- 

 matozoid (Fig. 242, B}. When the antheridium is mature its 

 wall ruptures when wet, and the sperm-cells escape in a mass 



