336 PHYSIOLOGY OF GROWTH AND CONFIGURATION 



furnish evidence concerning the chemical processes in plants. In this case the 

 leafy stem of a young sunflower plant (Helianthus annum) was cut ой a short 

 distance above the soil and to the cut surface of the stump was grafted a leafy 

 branch of the Jerusalem artichoke (Helianthus tuber osus). Union of the two 

 parts soon occurred and a new plant was formed. Examination of the sap 

 showed that the upper portion, down as far as the plane of the graft, contained 

 inulin in abundance, while the part below the plane of the graft contained starch 

 but no inulin. In this case the simple organic substances in the sap of both 

 portions were produced in the artichoke leaves above. In the reverse experi- 

 ment, where the upper part was sunflower and the lower Jerusalem artichoke, 

 a similar result was obtained; namely, that starch but no inulin was present in 

 the sunflower portion while the artichoke portion, which here received its simple 

 organic substances from the sunflower leaves, contained an abundance of inulin 



Fig. 173. — Three varieties of gourd grafted upon one another; a, ä fruits jaunes; b, poire verte; 



c, a fruits blancs. 



and even bore tubers, in which inulin accumulated in the same way as if the 

 whole plant had been of the artichoke species. Inulin clearly acts only as a 

 reserve carbohydrate. In both experiments the products of photosynthesis 

 were present in both stem and roots as glucose, but within the limits of the sun- 

 flower portion they accumulated as starch, while within the limits of the arti- 

 choke portion they accumulated as inulin. 



The operation of transplantation is successful only when closely related 

 species are involved, as may be understood from the foregoing discussion (page 

 329) of hormones and of the chemical differences between the metabolic sub- 

 stances of forms not closely related. 



