MOSSES 43 



bearing organ, and not until then, a change takes 

 place in the latter. Instead of shrivelling up 

 and dying, as it otherwise most assuredly would 

 do, its swollen base becomes more and more 

 swollen, owing to the growth inside of the young 

 spore-vessel, which has arisen from the special 

 fertilised cell (oosphere), and which is constantly 

 increasing in size, and ever tending to force its 

 way upwards towards the light. The pressure 

 which it thus exerts on the delicate walls of its 

 tiny prison at length becomes so great, that it 

 bursts through them, and rises up on a stalk 

 (seta) of its own, and generally bearing on its 

 end the upper portion of the fruit-bearing organ 

 inside which it was formed, which thus makes a 

 kind of covering for the young spore-vessel, and 

 is known as the Yeil or calyptra. The lower 

 portion, left behind, is the sheath, or vaginula. 



Eig. 10 of Plate III., taken from the Common 

 Wall Screw-moss (Tortilla muralis), to which 

 reference has already been made, affords a good 

 illustration of this, for on the end of the pale 

 yellow fruit-stalk will be seen the veil, looking 

 like a tiny extinguisher ; and under a low power 

 in the microscope we may get a glimpse, through 

 its thin, transparent walls, of the young, half- 

 formed spore-vessel inside, which, in this instance, 

 is in a very early stage of its development, and 

 is as yet hardly recognisable as a spore-vessel at 

 all. Towards the close of winter, or in the very 



