•24 



and known as perisperni, are found. D. S. Johnson" has 

 investigated the functions of the endosperm in many such 

 perisperm-yielding- plants, in its relation to the nourish- 

 ment of their sporoph\te generations, and the following 

 extract from his work gi\en in the " Morphology of 

 Angiosperms " is of interest and importance: - 



" Observations thus far made lead me to believe that 

 in the perisperm-containing seeds mentioned the embryo 

 sporophytc of the second generation is no\er nourislied b\- 

 the parent sporophyte directly, but always through the 

 intermediate gametophyte. In general, then, we find that 

 the food substance supplied to the embryo by the nucellus 

 may pass through the endosperm and be stored in the 

 embryo during the ripening of the seed, as in Cncurbita 

 and Phascoliis ; or, secondly, the food ma)- be stopped in 

 transit between the nucellus and the embryo and stored in 

 the endosperm, there to be held during the resting period 

 of the seed and delivered o\cr to the embryo only at the 

 time of sprouting, as in Riciiiiis, Zen, and apparently all 

 Gymnosperms ; or, finall}-, the food supply for the 

 develo]3ing embryo may be stored in the nucellus itself 

 until the time of germination, when it is passed on to the 

 embryo through the endosperm, as in Saiiniriis, 

 PcpcroiJiia, P/iy/olaccn, L a>iii<h and otliers." 



SUMMARY. 



1. The Microsporangia show but one primar\' 

 sporogenous cell in trans\'erse section ; the tapetum is 

 derived from the parietal cells ; the sporogenous cells 

 undergo 2-3 divisions before merging into spore mother- 

 cells ; the significance of the transition. 



2. The Megasporangium is of 7-g rows of cells ; the 

 hypoderraal cell of the central row is the archesporium ; it 



