BEYOPHYTA— MUSCI 117 



the summits of the shoots which produce the reproductive 

 organs. 



Besides these protonemal outgrowths leaf -buds are sometimes 

 formed which become detached and grow at once into moss 

 plants. They may arise on different parts of the plant, but 

 seem to be most easily developed upon root hairs. Some mosses 

 multiply by the separation of branches, or by the production of 

 stolons. 



Definite gemmas like those in the Marchantiacese are also of 

 frequent occurrence. They are stalked flattened bodies of more 

 or less circular shape, and consist of a single layer of cells. Many 

 of them are developed together at the end of a long support- 

 ing axis in Aulocomnion androgynum (fig. 876) ; in Tetrajihis 

 pellucida they are produced in a terminal cup, which is composed 

 of several leaves. When detached from the plant and transported 

 to moist soil they germinate, putting out a protonema, on which 

 a new gametophyte arises by the formation of a lateral bud. 



It is in the structure and development of the sporogonium 

 that the mosses chiefly show a great advance upon the liver- 

 worts. A sporogonium typical of most mosses is that of 

 Funaria hygrometrica, the structure of which may be examined 

 in some detail. 



The first division of the oosphere is, as before, caused by the 

 appearance of the basal wall, dividmg it into epibasal and 

 hypobasal segments. The latter takes little part in the subse- 

 quent development, not dividing more than once in most oases. 

 In some of the less highly organised mosses, such as Sphagnum, 

 it gives rise to a foot, but this absorbing organ in the higher 

 forms is developed from the end of the seta. 



The segmentation of the epibasal cell into octants is unusual. 

 Instead, by a succession of oblique divisions, an apical cell is 

 soon produced, and by the repeated division of this the embryo 

 grows. When it has reached a fair degree of development, 

 being fusiform in shape, the upper end swells to form the 

 capsule or theca, and the remainder continues elongating to 

 form the stalk or seta. As it elongates it ruptures the tissue of 

 the archegonial wall which still surrounds it. This breaks 

 across irregularly, and the withered neck with part of the venter- 

 wall is carried up by the elongating stalk and is recognised as 

 an easUy detachable cap over the capsule. It is called the 

 calypira(fig. 877, b o). 



When the capsule has become slightly swollen the tissue of 

 its substance differentiates into amphithecium and endothecium. 



