EEPEODUCTION OF ANGIOSPEEMIA. 770 



upper part of the nucleus {fig. 1118, c), to reach the mouth 

 of the canals of the corpuscula, one entering each {fig. 1119, b, 

 pt). At the same time, germinal corpuscles are produced at the 

 base of the secondary embryo-sacs {fig. 1119, b, a). These, after 

 fertilization, by the contact of the pollen-tube with the upper 

 end of the sac {pt), become cells, multiply, and form a celMar 

 mass, the lower cells of which break out through the bottom 

 of the endosperm, and grow as four cellular filaments (c), into 

 the substance of the lower part of the nucleus of the ovule ; at 

 the ends of these filaments, cell-division again occurs (d), and 

 from the apex of one of these filaments {suspejisors), is de- 

 veloped the embryo (d, em). As there are several corpuscles, 

 and each produces four suspensors, a large number of rudimen- 

 tary embryos are developed ; but usually only one of all these 

 rudiments is perfected. The embryo which is fidly developed 

 gradually increases in size, and most of the structures above 

 described disappear, so that the ripe seed exhibits a simple em- 

 bryo, imbedded in a mass of endosperm or albumen, the latter 

 originating apparently from the nucleus of the ovule." 



2. Bcprocluction of Angiospermia. — The structure of the pol- 

 len-cells of the Angiospermia has been already described (see 

 Pollen, and p. 772), and need not be fiu-ther alluded to in this 

 place. 



The ovule has also been particularly noticed, and we shall 

 now only recapitulate its component parts at the time when the 



Fig. 1120. 



Fig. 1121. 





Fig. IV. 



Fig. 1120. Vertical section of the orthotropous ovule of a species of Poly- 

 gonum, ch. Chalaza. n. Nucleus invested by two coats, m. Micropj le. 



s. Embryo-sac. c. Gerniiiial vesicle, or corpuscle. Fig. 1121. The 



ovule, some time before fertilization, a. The outer coat. b. The inner 



coat. s. The embryo-sac, with three nuclei at the upper end. Fig. 



1122. The internal parts of the ovule a short time before fertilization. 

 o.-Inner coat of the ovule, s. Embryo-sac. b. Germinal vesicle. After 

 Hofmeister. 



pollen is discharged from the anthers — that is, just before im- 

 pregnation takes place. It then consists of a cellular nucleus 

 {fig. 1120, n), enclosed generally in two coats, as in the present 



