DANIEL'S EXPERIMENTS AND CONCLUSIONS 165 



rot and parsnip show that the presence of reserve material is no 

 obstacle to success. Those of tomato on potato, annual sunflower 

 on Jerusalem artichoke, etc., show that the formation of tubers 

 on the stock takes place even when the cion is incapable of pro- 

 ducing tubers itself. In grafting in September a young cabbage on 

 a purple-topped turnip, which would have begun to thicken its root, 

 in October, the thickening came in the April following, when the 

 cion became plethoric. It is, then, the cion which by its mode of nu- 

 trition commands the function of reserve material in the stock. 



FIG. 141 SWELLINGS DUE TO GRAFTAGE 



1. Large growing apple on small growing stock. 2. Swelling of tissues at point 

 of union. 3. Pear on small growing stock. 



The inverse graft of plants susceptible of forming tubers on & 

 plant which does not yield tubers may be realized. Daniel suc- 

 ceeded in grafting Helianthns loetiflorns, a species with an enlarged 

 rhizome, on H. Animus, an annual species which does not form 

 tubers. <The cion grown entirely above the soil was unable to 

 form tubers. The reserves passed into another form in the stock, 

 which took a development altogether abnormal and became very 

 ligneous. Potato grafted on eggplant and on tomato has been ob- 

 served to form aerial tubers and thus store up its reserve material. 



215. Analogy in habitat seems to be a more or less important fac- 

 tor. Thus Phlox decussata, which grows in humid soils, has not 

 been successfully grafted by Daniel on P. subulata, which grows on 

 dry soils; though parsley, which prefers a dry soil, succeeds when 

 grafted with Sison ammonium, which prefers humid soil. In the 

 case of trees, pears are grafted on quinces in rich soil and on pear 

 seedlings in poor soil, etc. Different soils, then, are not the most 

 serious obstacles to success in grafting, but they seem to have more 

 or less marked influence on the duration of the graft. 



If a dormant ligneous cion is grafted on an active ligneous 

 stock, success follows, but does not follow if conditions are re- 

 versed. With herbaceous plants, an active cion may be grafted on 



