GRAFT-HYBRIDS. 571 



on the other those of the other parent. Thus the alleged graft-hybrid bears three 

 distinct sorts of flowers, and often parti-coloured combinations of the two parent 

 forms. The anatomical details of the tissues of the Adami-forms have been 

 examined and compared with those of the two parent-forms by Macfarlane. It 

 appears that the tissues show a remarkable mingling of the two parent-forms. In 

 some the one, in others the other parent-form predominates. Though in the 

 flowers (i.e. the pure Adami-fLowers) the mingling is quite consistent with its being 

 a well-balanced seed-hybrid, in the vegetative regions the strikingly diversified 

 intermixture of tissues is unlike that met with in any seed-hybrid hitherto 

 examined. It should be mentioned that where the Adami-pl&nt bears Laburnum 

 or purpureus shoots and flowers the anatomical characters of these shoots is 

 identical with the normal C. Laburnum and C. purpureus , respectively. Finally 

 the Adami-ftowers never ripen seeds (the ovules being malformed), though when 

 the parent-forms occur upon it they ripen fruit and seed. 



As a general rule the relations of the graft to the substratum (or stock) are very 

 different from those manifested in the case of Adam's experiment. The shoot de- 

 veloped from the ingrafted bud makes the same use of the substratum in which it 

 is imbedded as a parasite makes of its host-plant (see vol. i. p. 213). It procures 

 from the substratum a supply of " crude sap ", and this material is absorbed and 

 worked up by the protoplasts of the cells of the graft in the same way as the liquid 

 substances of the soil which are sucked up by roots. It must be premised that those 

 cells of the graft which take up the crude nutrient sap are adapted to their work in 

 very much the same way as are the suction-cells of roots, that is to say, they are able 

 to exercise a selective power, and only admit such substances as are good for the 

 species to which the scion belongs. Any influence that the substratum might have 

 on the graft could scarcely be other than such as would be exercised by soils of 

 various composition. At the most we should expect variations in shape and colour, 

 which have no permanence, and are not retained by the scion's posterity. As a 

 matter of fact, if, for instance, cuttings are taken from an Apricot-tree and grafted 

 on to various other Amygdalese, or are transferred from a Pear-tree to Quinces, 

 White-thorns, and other Pomaceas, they do not exhibit tf j slightest alteration in 

 fruit, flowers, or foliage after entering into organic union with the stock. Again, 

 when hybrid Roses produced by crossing are propagated by budding and grafting, 

 the result is the same whatever species of Wild-rose is taken for the substratum or 

 stock. In all the thousands of cases of propagation by these means none has been 

 observed in which the stock has had any essential influence upon the form of the 



scion. 



In 1876 and 1877 certain experiments were made in the Botanic Garden at 

 Innsbruck on the genus Iris. They were suggested by the fact of the production 

 of the hybrids of that genus already referred to, and consisted in grafting buds 

 from the root-stock of one species of Iris on to that of another species of the same 

 genus. The experiment was attended with perfect success, but the shoots and 

 flowers developed from the ingrafted buds showed no trace of any influence on the 



