1^6 PLANT PROPAGATION 



longer lived" than foster-rooted plants, and if "grafted plants of 

 all kinds are open to all sorts of accidents and disaster," then the 

 proposition should admit of abundant proof. The subject may be 

 analyzed by discussing the following questions: a. Is the union 

 always imperfect? b. Are grafted plants less virile, shorter lived 

 than own-rooted ones? 



a. It is well known that the physical union between cion and 

 stock is often imperfect and remains a point of weakness through- 

 out the life of a plant (201). But this is not always true. Scores of 

 plants make perfect physical union with other plants of their own 

 species, or even with other species. Therefore, these alone are the 

 plants that should be grafted. The best proof that can be adduced 

 that the union may be physically perfect, is in the micro-photograph 

 published by Prof. C. S. Crandall. [Similar ones are shown on 

 pages 138, 140.] The cells are knit together so completely it is im- 

 possible to determine the exact line of union. 



Professor Crandall also figures a microscopic section of an apple 

 graft in which the union is very poor, but this graft is made in a 

 different manner, another proof that operation should be suited 

 to subject. These were grafts made upon nursery stock. It would 

 appear that if the union were good at the expiration of the first 

 year it would remain good throughout the plant's life. In order to 

 test this point two apple trees 15 years old and over six inches in 

 diameter grafted at the surface of the ground in the nursery, were 

 split into many pieces in the presence of two critical observers, but 

 no mark whatever could be found of the old union. [Similar con- 

 ditions may be seen on page 148.] 



b. Are grafted plants shorter lived than others? It is evident that 

 a poor union or an uncongenial stock will make the resulting graft 

 weak, a further proof that indiscriminate graftage is to be dis- 

 couraged. But these facts do not affirm the question. 



Many persons hold that any asexual propagation is in the end 

 devitalizing, since the legitimate method of propagation is by means 

 of seeds. This notion appears to be confirmed by Darwin's conclu- 

 sions that the ultimate function of sex is really to vitalize and 

 strengthen the offspring following the union of characters or 

 powers of two parents; for if the expensive sexual propagation 

 invigorates the type, asexual propagation would seem to weaken it. 

 It does not follow, however, that because sexual reproduction is 

 good, asexual increase is bad, but rather that one is as a rule better 

 than the other, without saying that the other is injurious. Some 

 plants have been asexually propagated for centuries with appar- 

 ently no decrease of vitality. This fact, however, does not prove 

 that the plant may not have positively increased in virility if sex- 

 ual propagation had been employed. The presumption is always 

 in favor of sexual reproduction, a point which everyone will admit. 



Here is where graftage has an enormous theoretical advantage 

 over cuttage or any other asexual multiplication : the grafted 

 plant springs from sexual reproduction. If the union is physically 

 perfect, as is frequently the case, there is reason to suppose that 



