SOME TYPES OP PLOWEELESS PLANTS. 239 



295. Other Reproductive Apparatus. — The student cannot, with- 

 out spending a good deal of time and making himself expert in the 

 examination of mosses, trace out for himself the whole story of the 

 reproduction of any moss. It is sufficient here to give an outline of the 

 process. The protonema develops buds, one of which is shown in Mg. 

 206, and the bud grows into an ordinary moss plant. This plant, in the 

 case of the pigeon-wheat moss, bears organs of a somewhat flower-like 

 nature. Pig. 205, which contain either antheridia, Pig. 204, organs 

 which produce fertilizing cells called antherozoids, or archegonia, Pig. 

 203, organs which produce oospheres (§ 275); but in this moss antheridia 

 and archegonia are not produced in the same "moss-flower." The 

 plants therefore correspond to dioecious ones among flowering plants. 



After the fertilization of the oosphere, by the penetration of anthero- 

 zoids to the bottom of the flask-shaped archegonium, the development 

 of the oosphere into an urn begins, the latter rises on its slender stalk, 

 while the upper part of the archegonium is carried with it and persists 

 for a time as the hood. Pig. 202, c. 



MOSSES. 



296. Mosses have Specialised Organs. — In his examina- 

 tion of a moss the student at once recognizes it as a distinct 

 advance from the kind of plant life exemplified by any of the 

 cryptogamons types which he has previously studied. Boot, 

 stem, and leaf, as found in flowering plants, are represented 

 by organs of similar function, though not of similar structure 

 to true roots, stems, and leaves. The principle of physiological 

 division of labor, so characteristic of the higher plants, is 

 fairly exemplified in mosses. Although destitute of true 

 flowers, they possess flower-like organs which may be either 

 monoecious or dioecious. 



297. Alternation of Generations. — In mosses, as in the 

 simpler liverworts, below thenl, and the more complex ferns, 

 above them, the reproductive process includes what is known 

 as an alternation of generations. That is to say, the organs 

 of reproduction produce a spore which does not grow directly 

 into a new individual like the parent. The fertilized oosphere 



