454 



Cavers: Notes on Yorkshire Bryophytes. 



the seta. This elongation takes place in a few da3s and is due 

 simply to the rapid growth in length of the cells already formed, 

 the starch-grains being used up in the process and ultimately 

 disappearing. The dehiscence of the capsule takes place by 

 two, three, or four longitudinal slits extending from the apex to 

 the base. When there are two slits, each of the two valves 

 of the open capsule is notched (Plate, IV.). Sometimes the 

 dehisced capsule shows three valves, one notched, the others 

 entire (Plate, V.) ; or there may be four entire valves. In any 



Fig. 5. — I. Longitudinal section of perianth (Per.) with a nearly ripe sporogonium, enclosed in 

 its calyptra (Cal.)- Caps., capsule; Inv., involucre; Ar., unfertilised archegonium ; S., seta, 

 and F., foot of sporogonium. II. Part of transverse section through wall of young capsule. 



III. Similar section of mature capsule. IV. .Spore. V. Elater. I. x 25 ; II. and III. x 180; 



IV. and V. -X 250. 



case, the examination of the ripe but intact capsule shows that 

 the wall is marked by four longitudinal lines which meet at the 

 apex and in which the cells are relatively thin-walled. The 

 actual dehiscence may occur along all of these lines or only 

 along two or three of them. 



Naturalist. 



