PLANT LIFE. 



66. Protonema.--In its early stages the vegetative body 

 of the leafy liverworts and the mosses is either a flat thallus, 

 similar to the mature form of the thallose liverworts, or a 

 branching filamentous body, called the prolonema^ almost 

 identical with the form of the filamentous algae. Upon this 

 protonema the leafy shoot arises as a lateral bud, which soon 

 outstrips it in growth and differentiates leaves. The proto- 

 nema may live for some months, but generally perishes after 

 having produced a few leafy plants. 



67. Sporophyte.- -The non-sexual phase in the liverworts 

 and mosses has almost no vegetative functions, and a fuller 



a 



B 



G 



FIG. 72. .-/, two capsules of Bryum ; from the right-hand one the lid has fallen, 

 showing the teeth. Magnified 5 chain. B, four gametophyte shoots of Splachnum 

 ampullaceum, bearing four sporophytes. Natural size. C, a capsule of one of 

 the same sporophytes, showing enlarged apophysis, a, below the sporangium, j. 

 Magnified 10 diam. D, capsule of Splachnum liiteuin, with umbrella-like apo- 

 physis, , below sporangium, j. Magnified 2 diam. 



study of its structure is left for Part III. It consists at 

 maturity of a yellowish or brown spherical or cylindrical case 

 (fig. 72), which is sessile or raised upon a short or long 

 stalk and contains (a few or) hundreds or thousands of 

 reproductive cells called spores. The base of this stalk 

 constitutes an organ called the "foot,' which is embedded 

 in the gametophyte (f, fig. 73). 



68. Nutrition.- -The surface of the young sporophyte, 

 when large and well developed, as it is in the higher liver- 

 worts and mosses, is green. To a limited extent, therefore, 

 it is able to make food ; but not sufficient for its needs, 



