TEGETATJVE MULTIPLICATION 619 



The success of grafting depending on the contraction of intimate 

 union between the cellular structures of the two plants, it is not sur- 

 piising that, as a rule, it is only between nearly related plants that such 

 union is possible. If the size of the elementary organs, the rapidity or 

 the extent of their periodical multiplication and expansion, &c. are unequal, 

 it is evident that no permanent coherence can exist j a tissue grow ing 

 more rapidly w T ould tear itself away from one less active. As a general 

 rule, the elementary tissues agree closely in allied species, less closely in 

 genera of the same Order, and are very diverse in different Orders ; so 

 we find that grafts take readily on stocks of their own species, to a con- 

 siderable extent on stocks of allied species, and to some extent on stocks of 

 genera belonging to the same Order. As a general rule, genera of distinct 

 Orders cannot be grafted with success. The parasitic Mistletoe, however, 

 attaches itself by a natural graft to various trees, such, as Apples,_Oaks, 

 and even to Coniferae. 



Some as yet unexplained exceptions exist to the inclination to union 

 between allied genera. In some cases, also, a temporary union is effected, 

 subsequently destroyed by unequal growth. 



Among the Rosacese we see Pears grafted readily on Quinces, with more 

 difficulty on Apples, and not at all on Plums or Cherries. Cherries and 

 the Cherry-laurel readily unite. In the Oleacese we have the Lilac uniting 

 with the Ash, the Olive with Phillyrea. It is extensively practised also 

 with diverse species as well as varieties of Rhododendron. The Pear may 

 be grafted on the Hawthorn ; but the former grows so much faster than 

 the latter that the communication between the two becomes interrupted 

 in a few years at the point of junction. 



The practices of grafting and budding are principally carried on, like 

 propagation by slips &c., for the multiplication of varieties, which are, 

 for the most part, grafted on other varieties, or normal specimens of their 

 own species, these being far more healthy and permanent than those 



? rafted on allied species. The multiplication of esteemed varieties of 

 loses, fruit-trees, &c. is chiefly effected by this means, the object being to 

 produce specimens promising increased hardiness c., or to obtain size 

 and f ertility earlier than could occur in a plant raised from a small cutting. 

 Moreover, much greater certainty of reproducing the desired form is 

 attained than is the case with seeds. The seeds of an Apple, for instance, 

 rarely reproduce the parent form exactly. 



The Peach is worked on the Plum in Britain, because the latter is a 

 native of this climate and is stimulated to growth in spring by a lower 

 temperature than the Peach (from Persia) ; it does not succeed well here 

 on Almond-stocks. The Pear seems to succeed better on Quince than on 

 Pear-stocks in loamy soils ; and many similar instances are well known to 

 gardeners. In addition to these circumstances, Pears, Apples, and other 

 plants which may be easily grafted do not readily root from cuttings j 

 moreover esteemed varieties of Rose &c. are quickly multiplied as 

 " standards " &c. by budding them on briar-stocks already of several 

 years' growth ; and, in the case of new seedlings of fruit-trees, buds 

 inserted on full-grown stocks are brought to flower and fruit in a few 

 years, w y hile if left to grow up into trees alone, twenty years or more 

 might elapse before they bore a crop. 



Certain phenomena of grafting which are observed in practice cannot 



