178 SUMMARY OF CURRENT RESEARCHES RELATING TO 



(2) Nutrition and Growth (including- Germination, 

 and Movements of Fluids). 



Conditions for successful Grafting 1 .* — L. Daniel enters at great 

 length into the modus operandi and the rationale of successful grafting, 

 and insists first of all on a clear definition of terms. The term grafting 

 (greffage) must be limited to the operation itself, graft (greffe) to the 

 symbiosis of two or more plants. There are two distinct kinds of graft, 

 — grafts by approach or anatomical grafts, and grafts properly so called, 

 which are both anatomical and physiological. The latter may again 

 be divided into ordinary grafts and mixed grafts, the latter alone having 

 both an absorbing and an assimilating apparatus furnished both by the 

 subject (stock) and the graft. The graft by approach is said to be suc- 

 cessful when the two plants unite in a durable manner, so that their 

 separation destroys them ; a graft properly so called is successful when 

 the graft, developing upon the stock, produces fertile seeds. 



The conditions of successful grafting may be classed under two 

 heads, — extrinsic conditions, independent of the plants grafted; and 

 intrinsic conditions belonging ;to the species grafted. In grafting by 

 approach the absolutely necessary extrinsic conditions are : — (1) the 

 maintenance of the adhesion of the plants ; (2) a suitable temperature, 

 neither too high nor too low ; (3) the maintenance of the vitality of 

 the symbionts. In the case of grafts properly so called, three other 

 equally important conditions must be added : — (1) the maintenance of 

 the life of the graft and, of the stock up to a definite level ; (2) the 

 material possibility of the graft to re-establish the turgor which it has 

 lost in cutting ; (3) the necessity of never leaving, after the operation, 

 the level of the graft under water. The intrinsic conditions are the 

 mode of cicatrisation, analogy, and the parentage of the symbionts. By 

 analogy is meant such conditions as that one of the symbionts does not 

 produce a substance poisonous to the other; and that each of them must 

 receive a sufficient supply of food. 



The botanical parentage of the symbionts for successful grafting is 

 not subject to definite laws. Two species belonging to the same genus 

 or two closely allied genera of the same tribe, may be more difficult to 

 graft on one another than two species belonging to different tribes, as 

 occurs in the Solanaceas and Composite. This is evidently the result 

 of the fact that the dominating characters in classification are essentially 

 the reproductive characters. But analogy in the reproductive apparatus 

 does not necessarily go along with analogy in the vegetative apparatus ; 

 hence it may be easier to graft a species on one which differs more 

 widely from it than on one which more closely resembles it in the 

 characters which are ordinarily used for classification. 



Development of Etiolated Plants when replaced in the Light.f — 

 H. Ricome finds that etiolated plants, when again exposed to light, will, 

 in some cases, grow even more luxuriantly than under normal condi- 

 tions. This is ascribed to the larger stores of reserve food-material 

 contained in the longer stem and larger leaves of those individuals 

 winch have developed in the dark. 



* Rev. Gen. de Bot. (Bonnier), xii. (1900) pp. 355-68. 405-15, 417-55, 511-29. 

 Cf. this Journal, 1900, p. 693. f Comptes Rendus, cxxxi. (1900) pp. 1251-3. 



