340 PRACTICAL BOTANY 



single hypodermal cell, the archesporium, gives rise by division 

 to the spore-mother-cells, while the superficial layer of cells 

 which covers the archesporium divides into three, of which the 

 outermost alone remains as the wall of the mature sporangium ; 

 (3) that each of the spore-mother-cells divides into four cells, 

 which develop further into mature spores. 



THE GAMETOPHYTE, OR OOPHYTE 



The fresh spores may be sown on moist soil, and the first stages 

 of germination, which are rapid, may be easily observed ; the 

 later stages are, however, slow, and to see these the cultures must 

 be carefully kept. The result is the formation of prothalli 

 (oophoytes) of irregular form, some of which produce antheridia 

 after five to six weeks. Other prothalli, of larger size and more 

 complicated form, produce archegonia after about two to three 

 months. The antheridia are embedded in the tissue of the pro- 

 thallus, and produce large spermatozoids. The archegonia are 

 borne on the upper surface, and correspond in structure to those 

 of the Ferns. The result of fertilization of the ovum of the 

 archegonium is the formation of an embryo, which develops as the 

 spore-bearing plant or sporophyte. 



Endeavours should be made to obtain healthy cultures of the 

 prothalli of Equisetum, in which the above and other points may 

 be observed. 



