SELAGINELLA. OOPHORE. 173 



rangium is to develop macrospores, only one of these groups of 

 four cells is further developed, the rest being abortive ; if it 

 develop microspores, all the groups of four are further de- 

 veloped, 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 OOPHORE. 



XI. 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 enclosing oil globules and 

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

 thallium may be recognised 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 by 

 the potash, that a part of the contents of the spore is 

 traversed by a distinct network of cell-walls, forming a 

 meniscus-shaped mass of tissue. If plenty of spores 

 are to be had, it will be found better to embed a 

 quantity of them in cocoa-butter, and to cut sections, 

 and mount them in glycerine. Observe 



1. The character of the wall, consisting of 

 a. An outer thick, yellow Exospore. 



&. An inner thin Endospore. 



2. The contents as above described : the natural 

 position of the cellular tissue of the Prothallium may 

 be seen to be at the apex of the cavity of the spore. 



