1 10 MORPHOLOGY 



sporophyte. In considering the sporophytes of liverworts in general, 

 it is evident that from Riccia to Anthoceros there is a progressive sterili- 

 zation of sporogenous tissue, the steiilized tissue forming the vegeta- 

 tive structures. Among the Anthocerotales three additional features 

 of the sporophyte are noteworthy: (i) the beginning of independence 

 by the development of green tissue; (2) the beginning of sporangia by 

 the breaking up of a continuous sporogenous mass into separate smaller 

 masses ; (3) the establishment of a sterile axis by the transfer of the spo- 

 rogenous tissue to the outer region of the capsule, which suggests the 

 beginning of a region for the development of vascular tissues and the 

 beginning of superficial sporangia. 



It should be understood clearly just what is meant by such a state- 

 ment as that the Anthocerotales have certain features suggestive of the 

 pteridophytes. It does not mean that the pteridophytes have been 

 derived from the Anthocerotales or from any of the bryophytes. It 

 means simply that the sporophyte of the Anthocerotales represents 

 a stage of progress like one through which the pteridophytes may have 

 passed during their evolution. The plant groups as we know them now 

 certainly did not give rise to one another, but they can be used to sug- 

 gest general stages of progress, of whose real details and connections 

 we know nothing. 



2. MUSCI 



General character. This is the great group of bryophytes, both 

 in numbers and in specialization. "While the liverworts may be the 

 more interesting from the standpoint of suggestions as to pbylogeny, the 

 mosses are the representative bryophytes in our present flora. For so 

 great a group it is very well defined and consistent. Mosses are widely 

 distributed, being found in all habitats except salt water, and are 

 especially conspicuous in colder regions (alpine and arctic), where they 

 form a prominent feature of the vegetation. They seem to have been 

 derived from liverworts, and their sporophyte characters, at least, 

 suggest a possible connection with Anthocerotales ; while in certain 

 features of the gametophyte the resemblance to Jungermanniales is 

 more evident. Three groups are recognized: (i) Sphagnales, (2) An- 

 dreaeales, and (3) Bryales. 



(i) SPHAGNALES 



General character. These are the bog mosses, all of which belong 

 to the single genus Sphagnum. They are large, pale mosses, character- 



