GROWTH AND BRANCHING. 



47 



they form on the surfaces of leaves which fall to 

 the ground. Such detached buds, under favour- 



Fig. 55.— Formation of Buds on Fronds and Foliage-leaves. 



1, 2, on the pinnules of Asplenium hulbiferum; 3, on the margins of the lobes 

 the leaves of Bryophyllum calicinum. 



able circumstances of heat and moisture, throw 

 out roots, absorb moisture, and grow just as a 

 seedling plant would do (fig. 55). 



Gardeners avail themselves of this power of 

 independent growth in the striking of cuttings, 

 or in the raising of new plants from leaves 

 pegged down to the surface, as in Gloxinias. 

 The conditions favourable to the striking of 

 cuttings are essentially the same as those which 

 are propitious to the germination of the seedling 

 plants. 



When a cutting is taken a layer of impervious 

 cork-cells is formed over the wound, then a 

 callus is formed consisting of cambium or meri- 

 stem cells which grow actively, the cells in the 

 neighbourhood become filled with starch and 

 food-materials to supply the needs of the grow- 

 ing tissues, roots are formed, and thus the cutting 

 " strikes ". 



Grafting and Budding. — In these operations 

 the gardener removes either a single bud or 

 a shoot from one plant and inserts them into 

 another. If the operation be successfully carried 

 out adhesion takes place between the implanted 



bud or scion and the stock. No penetration or 

 mingling of tissues take place, but there is a 

 passage of fluid from stock to scion, and 

 from scion to stock. Possibly there may be 

 a passage of protoplasmic threads from one 

 to the other, but this has not been demon- 

 strated. 



The Inflorescence and the Bracts. 



When, as very often happens, the buds 

 destined to bear flowers are clustered to- 

 gether in one particular part of the branch 

 more or less separate or apart from the true 

 leaf-buds and shoots, that particular part of 

 the shoot or stem bearing flower -buds is 

 called by a distinct name — the inflorescence. 

 The buds of the inflorescence may be ar- 

 ranged just as the other buds are, but very 

 often they are arranged differently. The 

 principal things to be noted are: first, whether 

 the flower -bud or the developed flower is 

 solitary, at the end of a stalk (terminal), as 

 in the tulip; or lateral and axillary, as in 

 the periwinkle, Vinca. If the flowers are 

 more than one, then it is necessary to note 

 their precise arrangement, and in particular 

 to observe the order in which they are pro- 

 duced; thus, in some cases the lowest flower 

 of a long group is formed first, and opens 

 first, being followed in succession, from 

 )f below upwards, by the others, as in the 

 wallflower. Such an inflorescence is called 

 indefinite, because its flowers may go on expand- 

 ing in the same order so long as 

 growth goes on at all (fig. 56). 

 When, however, the topmost 

 or the central flower of a cluster 

 expands first, and the others 



Fig. 56.— Racemose Inflo- 

 rescence—Indefinite. 



Fig. 57.— Cymose Inflorescence— Definite, 

 the central flower opening first. 



in succession from above downwards, then the 

 term definite inflorescence is used (fig. 57). The 



