56 STRUCTURAL AND PHYSIOLOGICAL BOTANY. 



of tke amnios, containing a fluid named the liquor amnios, 

 among which the emhryo is developed. 



XV. IMPREGNATION. 



466. Impregnation is effected by contact between the 

 pollen (378) and the stigma (397). 



467. The pollen ci emits a tube" of extreme delicacy, 

 which pierces the stigma 6 and style 51 , and, passing downwards 

 into the ovary /A , enters the foramen (461) of the ovule" l . 



468. Having reached the foramen, it comes into contact 

 with the nucleus (450). 



469. This accomplished, the act of impregnation is over; 

 a new body gradually appears in the sac of the amnios (465), 

 and eventually becomes an embryo. 



470. Great numbers of modifications of this phenomenon 

 have been observed, but they^ all resolve themselves into these 

 facts. 



471. In plants, the ovules of which have no pericarpial 

 covering, such as Cycadaceae and Coniferse, (gymnosperms,) 

 the pollen falls in the foramen, and there acts as" if it had 

 struck the stigma. 



472. If only one pollen tube enters an ovule, there is but 

 one embryo in the seed. But if several pollen tubes pass into 

 the same ovule, there may be several embryos in the same 

 seed ; Ex. Onion, Miseltoe. 



