i8 THE STORY OF PLANT LIFE 



and placed upon another stem or stock, the new bud 

 becoming eventually part of the stock upon which it 

 is inserted. (See Fig. 6.) 



A graft or scion is obtained by inserting a shoot 

 with buds in a similar manner upon a stock. The 

 scion and the stock each exhibit and retain their own 

 individual characteristics. A graft-hybrid is one in 

 which the characters of scion and stock become 

 blended. Recently doubt has been thrown upon 

 their existence as such. 



Turning now to the process of reproduction, pure 

 and simple, by sexual methods, we have to deal with 

 the union of a male cell with a female cell, and after 

 fusion the resulting new cell or product of the two. 

 (See Fig. 7.) 



The original male gametes are formed in the pollen- 

 grains furnished by the stamens, often called the male 

 organs. The pollen-grains are contained in pollen- 

 sacs or microsporangia and equal the microspores of 

 lower types of plants, and each pollen-grain contains 

 the two nuclei, the one vegetative, the other gene- 

 rative or the male, or sperm -cell. The female repro- 

 ductive cell is furnished by the ovule or megaspor- 

 angium, and the egg-cell is the ovum or oosphere. 

 The embryo-sac is the megaspore. The result of 

 fertilisation is the growth of the embryo, which forms 

 with adjacent structures in the ovule, the seed, a 

 characteristic of Spermatophytes. 



The embryo is a dormant sporophyte, derived from 

 a reduced oophyte. The endosperm represents the 



