272 PRACTICAL BOTANY 



in glycerine. The following points in the process of development 

 may be observed : The sporangium is first seen as a swelling of a 

 group of cells at the surface of the apical cone, above the leaf in 

 the axil of which it appears : thus the sporangium is not borne 

 on the leaf as in Lycopodium, but springs from the tissues of the 

 axis. A central row of cells grows more strongly than the rest, 

 and the outermost cell but one of this series may be recognized as 

 the archesporium. The outermost cell divides to form part of 

 the two outer layers of the wall of the sporangium. The arche- 

 sporium also divides to form a mass of tissue, of which the 

 peripheral layer becomes the tapetum (the basal part of the 

 tapetum is however derived from the adjoining tissue). The 

 central part of the tissue derived from the archesporium forms the 

 spores : each spore-mother-cell separates from its neighbours, and 

 divides into four cells. If the sporangium is to develop macro- 

 spores, only one of these groups of four cells is further developed, 

 the rest being abortive ; if it form microspores, all the groups 

 of four are further developed, but only attain a comparatively 

 small size : in both cases the four spores may separate from one 

 another when quite mature,' though they often retain their original 

 arrangement. 



THE GAMETOPHYTE OR OOPHYTE. 



XL Spores of both kinds may be obtained free by 

 drying branches which bear sporangia on sheets of 

 paper. Pick out the macrospores, and mount them 

 in olive-oil : dissect off the brittle outer coat of the 

 spore with needles, and examine under a high power. 

 It will be seen that the chief contents of the ripe spore 

 are a protoplasmic matrix inclosing oil-globules and 

 aleurone-grains, while traces of the cells of the pro- 

 thallium may be recognized even in these preparations. 



Prepare other such spores with potash, and dissect as 

 before, or press on the cover-slip, and warm gently. It 

 will be found, when the oil, &c., has been acted upon 



