iv. THE ANTHOCEROTES 121 



the ground in shady and moist places, and are usually not 

 well adapted to resist dryness. 



The chloroplasts in the Anthocerotaceae resemble those in 

 certain confervoid Algae, e. g., Stigeoclonium, Coleochcete. 

 Each cell in most species shows a single large chloroplast con- 

 taining a pyrenoid. In sterile specimens of an undetermined 

 species of Anthoceros from Jamaica, two chloroplasts were 

 found in each cell, and a doubling of the chloroplast is not un- 

 common in the more elongated thallus-cells of other species, 

 while in the sporophyte there seem to be regularly two chloro- 

 plasts in each cell. Simple thin-walled rhizoids are formed 

 abundantly upon the ventral surface, where there are in many 

 species curious stoma-like clefts which open into cavities filled 

 with a mucilaginous secretion, and in some of which, in all 

 species yet examined, are found colonies of Nostoc which form 

 dark blue-green roundish masses, often large enough to be 

 readily detected with the naked eye, and which were formerly 

 (Hofmeister (i), p. 18) supposed to be gemmae. 



The sexual organs are very different from those of the 

 true Hepaticae, and are more or less completely sunk in the 

 thallus from the first. While the first divisions in the 

 archegonium are much like those in the Hepaticae, the subse- 

 quent ones are much less regular except in the axial row of 

 cells, and the limits of the outer neck-cells are in the subsequent 

 stages difficult to determine, and the archegonium projects 

 very little above the surface of the thallus, even when full 

 grown. The divisions in the axial row of cells correspond to 

 those in the other Archegoniatae. 



The origin of the antheridium is entirely different from 

 that of all other Bryophytes, but shows, as will be seen later, 

 certain suggestive resemblances to that of the lower Pteri- 

 dophytes. Instead of arising from a superficial cell, as in all 

 of the former, the antheridium, or in most cases the group of 

 antheridia, is formed from the inner of two cells arising by the 

 division of a superficial one. The outer one takes no part in 

 the formation of the antheridia, but simply constitutes part of 

 the outer wall of the cavity in which they develop. 



While the gametophyte is extremely simple in structure, 

 being no more complicated than that of Aneura or Metzgeria, 

 the sporophyte reaches a high degree of complexity. Here, 

 instead of the greater part of the sporophyte being devoted to 



