3 o VASCULAR CRYPTOGAMS 



stouter pedicels, and arise from the apex of the columel. In the forma- 

 tion of the pedicels of the megasporanges longitudinal cell-division takes 

 place, as well as transverse. The mode of formation of the spores 

 within each kind of sporange has already been described in general 

 terms, after the preliminary separation of a single external layer of cells 

 which develops into the wall of the sporange. The sixty-four micro- 

 spores appear to be disposed without any arrangement in the cavity of 

 the microsporange. A large nucleus lies at the end of the megaspore 

 which is nearest the apex of the sporange. Before fertilisation both 

 kinds of sporange become detached from their pedicels, and are carried 



FIG. 13. Massula of Azolla Caroliniana Willd. (X24o). (After Strasburger.) 



up to the surface of the water in the spring by the surrounding masses 

 of Algae. The epi spore then splits above the apex of the megaspore 

 into three lobes, between which the emerald-green prothallium forces 

 itself, and impregnation is effected. In Azolla the epispore assumes a 

 still more striking form. In the microsporanges it has the appearance 

 of a large-celled tissue, and breaks up into two or more spherical masses 

 called massulce, each of which envelops a number of microspores, and 

 has a distinct coat. In some species, but not in all, the surface of these 

 masses is covered with hair-like appendages, barbed at the apex, the 

 glochids, by means of which, after emerging from the sporange, and 

 when floating on the surface of the water, they attach themselves to the 



