MOSS. SPOROPHORE. 9 



posed of a single layer of cells arranged in four to six 

 rows : these surround a central canal, which is filled 

 with mucilage at the time of fertilisation, but before 

 maturity there may be seen within it a series of 

 canal cells. 



2. A lower, enlarged ventral portion, consisting of 

 two layers of cells, which constitute the "wall, and 

 inclose a central space, in which may be seen the 

 naked spherical oosphere or ovum, and above it (up 

 to the period of maturity) the smaller ventral canal 

 cell. 



Similar sections, similarly prepared from rather older speci- 

 mens, may show as the first results of fertilisation that the neck 

 of the archegonium turns brown and withers, while the wall of 

 the ventral portion and the stalk show considerable increase in 

 bulk, and frequent cell-divisions. Meanwhile growth and cell- 

 division take place also in the fertilised ovum, resulting ulti- 

 mately in the development of the sporogonium : the growth of 

 the wall of the archegonium keeps pace for some time with that 

 of the young sporogonium, completely inclosing it, but as it in- 

 creases towards maturity, the wall of the archegonium is ruptured 

 transversely about half-way up : the apical part is carried up- 

 ward by the growing sporogonium, as the calyptra which covers 

 its apex, while the lower portion remains as an investment of the 

 base of the seta, and is called the veil or vaginula. 



Note especially in young sporogonia the two-sided, wedge- 

 shaped apical cell, with segments cut off from either side. 



Sporophore Generation. 



The Sporogonium. 



X. Having noted the external characters of the 

 sporogonium of Polytrichum, as above described, 

 cut transverse sections of the mature seta : mount in 



