268 



THE SPORE-PRODUCING ORGANS 



[CH. 



segmentation usual for Leptosporangiate Ferns. The number of the spore- 

 mother-cells in the microsporangia is i6, and accordingly the spore-number 

 is 64, all of which are normally developed as microspores. In the mega- 

 sporangia there are only 8 spore-mother-cells, the last division having been 

 omitted. The potential number of megaspores is therefore 32, but only one 

 of these is matured. A double layer of tapetum is laid down, which merges 

 into a nucleated plasmodium, from which extraordinary developments arise 

 in relation to the megaspore. The two types of sporangia which result are 



seen in Figs. 262 



epresents a single ripe microsporangium 



Fig. 263. Megaspoiang'mm and Megsispore of A2o//a^/it:u/ozcfes, 

 Lam. .-/ shows a megaspore in longitudinal section sur- 

 rounded by the complete indusium. ^ = a megaspore suspended 

 in the upper half of the indusium : the massulae {msl) are attached 

 firmly by their glochidia {£■/) to the epispore with its many fine 

 hairs, i. = indusium •,ep. = epispore ; sw. — swimming apparatus ; 

 jr/. = residue of the sporangial wall, which in A still covers the 

 swimming apparatus within the apex of the indusium : in B it 

 has assumed a funnel-shape. ( x 75.) (After Strasburger, from 

 Engler and Prantl.) 



of Azolla containing a number of " massulae," each of which is a clump of 

 periplasmic material including many microspores. These massulae may be 

 set free separately into water, and being provided with anchor-like processes, 

 or " glochidia," they attach themselves to the rugged surface of the mega- 

 spore (Fig. 263). The latter is of large size, and like the rest of the spores it 

 is tetrahedral in form, and it lies in the sporangium with its apex directed 

 upwards, that is away from the stalk. Each megasporangium is surrounded 

 by a flask-shaped indusium, which envelopes it completely except for a 



