REPRODUCTION OF ANGIOSPERMIA. 



'61 



the placenta or placentas, and then come into contact with the 

 ovules. One or sometimes two of these pollen-tubes enter into 

 the micropyle of each of the ovules {figs. 1115 and 1116), by which 

 it reaches the nucleus and embryo-sac. When it reaches the 



1115. 



-ig. 1116. 



Fig. 1115. Section of the ovule of a species of CEnothera. t. Enlarged end of 

 pollen-tube containing fovilla, whiich has entered the micropyle, and is seen 

 pressing inwards tlie apex of the embryo-sac. sr. Impregnated germinal 

 ■vesicle, which already begins to exhibit two parts ; one, the upper, forming a 

 suspensor, s, and another, below, r, a globular body, which ultimately be- 

 comes the embryo, e. Endosperm cells or albumen. Fig. 1116. Section of 



the ovule of a species of Orchis, t. Enlarged end of the pollen-tube which 

 has passed through the micropyle, and is closely applied to the embryo-sac, 

 the upper side of which it has pushed inwards, e. Germinal vesicle in the 

 interior of the embryo-sac in an impregnated state, and dividing into two 

 portions, the lower of which is the rudimentary embryo, and the upper 

 forms a suspensor, 



latter it is generally somewhat enlarged (figs. 1 1 15, f, and 1116, t), 

 and adheres firmly to it at or near its apex {figs. 1115 and 1116). 

 The embryo-sac is frequently introverted to a slight extent at 

 the point of contact with the pollen-tube {figs. 1115 and 1116), 

 and it is stated by Hofmeister, to perforate it in Canna, but if such 

 a perforation occurs in this case, it is altogether an exception to 

 what is generally observed. As soon as contact of the pollen-tube 

 and embryo-sac is effected, a kind of conjugation, or endosmotic 

 action between the contents of the two, takes place, the result of 

 which is the development of one, or rarely two, as in Orchis and 

 Citrus, or more, of the germinal vesicles, into embryos. Accord- 

 ing to Henfrey, as previously noticed (see p. 759), the first 

 change is the development of the germinal corpuscle into a 

 germinal vesicle or cell. 



The germinal vesicle in its development into an embryo, gene- 

 rally divides in a transverse manner into two cells (fig. 11 16, e); 

 the upper of which by elongating, and frequently by further 



