6o Report of the Microscopical Section. [Sess. 



spore-producing tissue, from which arise the spore mother- 

 cells ; each of these spore mother-cells ultimately divides into 

 four, thus forming four microspores, which, when ripe, are 

 liberated by the rupturing of the sporangium. When these 

 microspores fall on damp ground they at once begin to 

 germinate, and ultimately each one produces a spermatozoid, 

 which is set free by the walls of its mother-cell becoming 

 dissolved. The macrosporangium also gives rise to a mass of 

 spore-bearing tissue, which in turn forms spore mother-cells, 

 of which, however, only one comes to maturity. This one 

 divides into four daughter-cells, which in the end absorb all 

 the other mother-cells. Each of these daughter-cells gives 

 rise to a macrospore. These macrospores begin to germinate 

 while still in the sporangium, and the completion of the 

 germination is carried on after the spores have fallen to the 

 ground. 



The tissue in the macrospore which the germination pro- 

 duces is called the prothallus, and this prothallus gives rise 

 to the archegonia or female organs. The archegonia become 

 mature about the same time that the spermatozoids are set 

 free from their mother-cells. If then there be water on the 

 ground, and some of the spermatozoids are brought within the 

 influence of an archegonium, one of them will penetrate the 

 neck of the latter, and thus reach the ovum in the arche- 

 gonium and fertilise it. This fertilised ovum gives rise to the 

 embryo of the new Selaginella plant, which in turn again will 

 bear the microsporangia and macrosporangia. 



The second type studied was one of the Filices — the As- 

 pidiuni Filiv-mas. In this fern the spores are produced in 

 sacs called sporangia, grouped together in clusters called sori 

 on the under-side of the pinnules of the fronds. Unlike the 

 spores of the Selaginella, the spores of the Ferns are all 

 of one kind, so that these plants are homosporous. When the 

 spores are ripe, the sporangium bursts at a particular place and 

 sets them free. If they fall on damp soil, they soon begin to 

 germinate. The first appearance of germination is the forma- 

 tion of a root-hair which grows downwards into the ground ; 

 this is followed by another outgrowth called a prothallus, 

 which grows upwards towards the light. As the prothallus 

 increases in size it changes its vertical position to a horizontal 



