ro 



MOSSES AND FERNS chap. 



and among the Mosses similar ones are common in Tctraphis 

 and some wiher genera. 



The archegonia of all the MuscinecX agree closely in their 

 earlier stages, but differ more or less in the different groups at 

 maturity. In all cases the archegonium arises from a single 

 superficial cell, in which three vertical walls are formed that 

 intersect so as to form an axial cell and three peripheral ones. 

 From the axial cell develop the ^gg, canal cells, and cover cells 

 of the neck, and from the peripheral cells the wall of the venter 

 and the outer neck cells. In all IMuscinCcne except the Antho- 

 cerotes the archegonium mother cell projects above the sur- 

 rounding cells, but in the latter the mother cell does not project 

 at all, and the archegonium remains completely sunken in the 

 thallus. In all other forms the archegonium is nearly or quite 

 free, and usually provided with a short pedicel. This is espe- 

 cially marked in the Mosses, where the lower part of the arche- 

 gonium is as a rule much more massive than in the Hepaticae. 



The most marked difference, however, between the arche- 

 gonium of the Hepaticse and Mosses is in the history of the 

 cover cell or uppermost of the axial row of cells of the young 

 archegonium. This in the former divides at an early period 

 into four nearly equal cells by vertical walls, the resulting cells 

 either remaining undivided, or undergoing one or two more 

 divisions ; but in the Mosses this cell functions as an apical cell, 

 and to its further growth and division nearly the whole growth 

 of the neck is due. 



The antheridia, except in the Anthocerotes, also arise from 

 single superficial cells, and while they differ much in size and 

 form, are alike in regard to their general structure. The 

 antheridium always consists of two parts; a stalk or pedicel, 

 which varies much in length, and the antheridium proper, made 

 up of a single layer of superficial cells and a central mass of 

 small sperm cells. The former always contain chloroplasts, 

 which often become red or yellow at maturity. The sperm 

 cells have no chlorophyll, but contain abundant protoplasm and 

 a large nucleus, which latter forms the bulk of the body of the 

 spermatozoid found in each sperm cell of the ripe antheridium. 

 The spermatozoids are extremely minute filiform bodies, 

 thicker behind and provided with two fine cilia attached to 

 the forward end. Adhering to the thicker posterior end there 

 may usually be seen a delicate vesicle, which represents the 



