MOSSES AND LICHENS OF THE PACIFIC COAST. 69 



In Europe, this species, in common with others, produces quite com- 

 plex sex organs, but in this country they have not been observed on 

 Lunularia, though they may be found on wild species. In places where 

 ferns grow from the spore, a fern prothallium may easily be mistaken 

 for a very small liverwort. 



Marchantia polymorpha is another species of liverwort found in many 

 parts of the world, and is similar in its habits of growth to the last- 

 mentioned variety. On the ledges which border the brooks in the Santa 

 Cruz Mountains, notably along Boulder Creek, may be seen most inter- 

 esting patches of liverworts, sometimes covering several square feet 

 of surface. Their flat manner of growth, their two-forked mode of 

 branching, and their green color easily distinguish them from other 

 lowly plants found in similar situations. 



On cool, shady banks, in the early spring, specimens of Asterella 

 Californica, or the Star Liverwort, may often be found by those who 

 are looking for the less obvious products of the soil. From a little 

 forked leaf-body, the size perhaps of your finger-nail, rises a little 

 four-lobed umbrella, which contains a part of the sex organs, which 

 are concerned in the formation of germs for the propagation of the 

 species. 



Other liverworts are somewhat leafy in form, and resemble the 

 true mosses, for which they may easily be mistaken. Some of them 

 live on the bark of trees, and curl up and lie dormant during the long, 

 dry summer. 



The true mosses, though lowly plants, bear distinct leaves, and have 

 a unique method of reproduction. Take for example a specimen of 

 Polytrichium, one species of which is familiarly known as Robin's Rye. 

 The plant, as ordinarily seen, resembles a miniature evergreen tree, 

 two inches high. There is a brown trunk and radiating green leaves. 

 From the top of this tree extends a slender rod, on the top of which 

 is a peculiar capsule, shaped somewhat like a kernel of rye. This 

 capsule contains numerous grains of dust, each one of which is an 

 asexual spore, capable of producing a moss plant, if it falls on suitable 

 soil. The moss plant, however, is at first very unlike that from which 

 the spore came, being a minute, thread-like plant, called a protonema. 

 From this protonema grows the long stalk, near the summit of which 

 are developed the true sex organs. In one of these organs is an 

 egg-cell which becomes fertilized by a sperm cell, and straightway it 

 begins to grow. As it grows, it forms the slender rod with the urn- 

 shaped capsule upon the top, in which are the spores; and now the 

 circle of moss life is complete. Alternation of generations is distinct 

 and evident, but the spore-bearing plant is small, while the sexual 

 phase is comparatively large and conspicuous. As we pass to higher 



