402 



BOTANY. 



which multiply by fission, and eventually unite into a con- 

 tinuous tissue (in reality a false tissue), the endosperm (en, 

 Fig. 297, B). In this mass of endosperm cells several near 

 the micropylar end grow larger than the surrounding ones, 

 and become filled with granular protoplasm. These are the 



corpusc-ula of Brown, the 

 archegonia of Sachs, or 

 the secondary embryo sacs 

 of Henfrey (cp, cp, Fig. 

 297, B}. In some cases 

 they are placed singly at 

 short distances from each 

 other, while in others they 

 are clustered together 

 (1 and 2, Fig. 298). Each 

 corpusculum is at first a 

 single cell, but when fully 

 developed it consists of an 

 elongated cell, the germ- 

 cell proper, and, in many 

 cases at least, one or more 

 neck-cells, the whole sunk- 

 en deeply into the sub- 

 Pig. 298 1. Three corpuscuia. cp. of jum- stance of the endosperm. 



pentf communig, close together, and seen in a , i -i i , i 



longitudinal section of the ovule ; ei, the first I he neCK IS lOrmed by the 



suspensor cells of two fertilized eorpuscula , , . . . , 



at the upper end of the corpuscula are i-hown Cutting Oil Ot a portion OI 



the neck cells ;, the lower end of the pollen ,1 n -\ __n _.c 4.1,-. 



tube. 2. A sinillar section taken a little later ; the Original Cell OI the COr- 



n 



cases 



aSsssy^ {i remains sin s le ' while in 



cleu8,"M, of the ovule, shown in outline; , others it divides SO as to 



endosperm in enlarged embryo sac ; e', portion 



of endosperm broken up ; cp. three corpus- lorm a Vertical TOW, and 



cula, from the lower ends of which the suspen- , , 



sors, v, grow ; p, pollen tube. 1 and 2 X 200 ; in others a IOU1*- Or 6V6n 



3 X 100 ; 4 X 50.-After Hofmeister. 



plane (see Fig. 298, 1) ; the latter arrangement has been 

 termed a rosette. 



511. If we now review the structure of the ovule its ho- 

 mologies can be readily made out. The ovule itself plainly 

 corresponds to the macrosporangium of the higher Pterido- 

 phytes, and the embryo sac is to be regarded as the homo- 



