610 



APPENDIX A 



midribs, and in the fact that the spore capsule (sporophyte generation) is either 

 retained within the archegonium or, if emergent, lacks a cap. In the temperate 

 zones leafy liverworts are not numerous; but in the perpetually moist cloud 

 forests of tropical America (Fig. 33.16) they and other similarly delicate plants 

 cover the tree trunks, lianas, and rock surfaces with an inches-thick growth that 

 holds water like a sponge. 



The Mosses (Musci) represent a higher level of bryophyte organization. They 

 have been described in Chap. XIII, and their life cycle was discussed in Chap. XVII 

 (Fig. 17.4). They are world-wide in distribution and grow in every kind of habitat 

 from aquatic to dry. Like the liverworts most of them are small, but they tend to 



Fig. A. 12. Representative mosses. Left, a true moss, Aulacomnium palustre, showing the 

 leafy gametophyte and the bare stalks and capsules of the sporophyte. Right, a bog moss, 

 Sphagnum. In this group the gametophyte plant includes not only the leafy stems but 

 also the sporophyte-bearing stalks; the small sporophytes are ovoid capsules with a very 

 short foot. When the spores are mature, the round lid of the capsule pops off. (Left, courtesy 

 General Biological Supply House, Inc.; right, photo by Prof. E. B. Mains.) 



grow in dense masses which may, as in the case of sphagnum, form hummocky 

 growths covering a large expanse. Those that grow on the ground have no under- 

 ground parts except the rhizoids, so that moss mats may easily be stripped from 

 the substratum. Mosses have true leaves and a stem with a central strand of 

 vascular tissue. Although many of them occur in dry situations, they require 

 water for sexual reproduction, since — like the liverworts — they have swimming 

 sperms. The sporophyte generation is more conspicuous than in the liverworts, 

 but it is parasitic on the gametophyte; it produces a spore case with a cap that 

 pops off to release the spores. 



Phylum III. TRACHEOPHYTA (trak e of it a; Greek, trachia, 

 "trachea," "windpipe," and phijton, "plant"). The Vascular Plants. 



