244 



Cavers : Notes on Yorkshire Bryophytes. 



voung receptacle. The writer's observations lead rather to the 

 conclusion that the receptacle is derived directly from the grow- 

 ing- point, and that the latter is used up in the process. In the 

 crescent-shaped receptacles, the youngest antheridia are found 

 at the ends of the two anterior horns, on either side of the sinus 

 (Fig. 5, C). This can hardly be interpreted otherwise than as 

 the result of branching of the growing-point during the develop- 

 ment of the receptacle. Moreover, in longitudinal sections 

 through a very young receptacle, in which only a few young 

 antheridia have been formed, there is no trace of the projec- 

 tion described by Leitgeb as invariably occupying the front of 

 a receptacle and representing the growing-point of the shoot. 

 At a later stage an outgrowth of this kind is present, and 

 undoubtedly represents the beginning of an adventitious shoot, 

 which remains dormant during the development of the receptacle 

 but may afterwards grow out and give rise to an innovation- 

 shoot. The male receptacle of Rehoiilia may therefore be 

 regarded as representing a branch, having on its anterior 

 margin a single growing-point, or, in many cases, two growing- 

 points. Apart from the fact that the branching in the latter 

 case takes place at a late stage, after several antheridia have 

 been formed, and occurs once only, giving rise to a crescent- 

 shaped receptacle, there is no essential difference between the 

 receptacle of Rehoiilia and that of Fegatella, in which the 

 branching takes place at an earlier stage and is repeated 

 several times, giving rise to radiating rows of antheridia. 



The ANTHERiDiUM is usually pear-shaped, tapering above to 

 a pointed beak ; the stalk is very short, and the wall consists 

 of a single layer of large oblong cells. The compact tissue in 

 the lower part of the receptacle, between the antheridia, consists 

 of colourless cells. This tissue is highly mucilaginous and 

 swells up on the addition of water. The cells forming the 

 antheridium-wall and the antherozoid mother-cells are also 

 mucilaginous, and the absorption of water by these tissues leads 

 to considerable swelling and consequent pressure, resulting 

 frequently in the forcible expulsion of the antherozoids from the 

 pores on the surface of the receptacle. These explosive dis- 

 charges are not so marked in Rehoiilia as in some other 

 Marchantiace^e in which they have been observed ; the writer 

 has, however, observed the jets of antherozoid-containing spray 

 to rise to a height of about 5 cm. in Rehoiilia. 



The FEMALE RECEPTACLE arlses as a dorsal outgrowth imme- 

 diately behind the apex of the branch (Fig. i, B, C). The 



Naturalist, 



