444 SUMMAKY OF THE CHAPTER. Chap. XL 



alone. By following with perseverance this plan during 

 three or four successive seasons, a distinct and fixed variety 

 can generally be secured. 



Finally, the facts given in this chapter prove in how close 

 and remarkable a manner the germ of a fertilised seed and 

 the small cellular mass forming a bud, resemble each other in 

 all their functions — in their power of inheritance with occa- 

 sional reversion,— and in their capacity for variation of the 

 same general nature, in obedience to the same laws. This re- 

 semblance, or rather identity of character, is shown in the 

 most striking manner by the fact that the cellular tissue 

 of one species or variety, when budded or grafted on another, 

 may give rise to a bud having an intermediate character. 

 We have seen that variability does not depend on sexual 

 generation, though much more frequently its concomitant than 

 of bud reproduction. We have seen that bud-variability 

 is not solely dependent on reversion or atavism to long -lost 

 characters, or to those formerly acquired from a cross, but 

 appears often to be spontaneous. But when we ask ourselves 

 what is the cause of any particular bud- variation, we are lost 

 in doubt, being driven in some cases to look to the direct 

 action of the external conditions of life as sufficient, and in 

 other cases to feel a profound conviction that these have played 

 a quite subordinate part, of not more importance than the 

 nature of the spark which ignites a mass of combustible 

 matter. 



