8. COHESION AND ADHESION. 



Jl 



growth.) The pseud -axis which is thus formed is at first crooked, 

 but in most cases it subsequently becomes straight (Fig. 11 A 

 becomes B\ If the stronger growth always occurs in the lateral 

 shoots of the same side, the system is called a helicoid cyme (Fig. 

 11 D) ; if alternately in those of both sides,- it is called a scor- 

 pioid cyme (Fig. 11 A,B). Such a branch-system is said to be 

 sympodial. 



As examples of these various modes of branching, the inflorescences, 

 which will be treated of subsequently (Part IV.), may be especially men- 

 tioned; the following are selected from the vegetative organs: 



Racemose branching 'is very evident in Conifers ; the trunk is always 

 more strongly developed than its lateral branches, and these than their 

 lateral branches. 



False Dichotomy is exhibited in the stem of Viscum, the Mistletoe, the 

 apex of which either terminates in a flower or else dies ; only the axillary 

 buds of the two leaves develope into new annual shoots. As regards - 

 the arrangement of the annual shoots, the same occurs in Syringa, the- 

 Lilac, in which the axillary buds of the uppermost pair of leaves form 

 the continuations of the stem, whilst the terminal bud dies; also in 

 filiamnus cathartica, in which the- main axis is metamorphosed into a^ 

 thorn. In this case the branching of each annual shoot is racemose, but 

 the successive annual shoots form a cyme. 



The succession of the annual shoots of many trees, as the Birch, Elm, 

 Beech, and Hazel, affords examples of the sympodial cyme; in these, each 

 annual shoot either terminates in a 

 flower, or it dies, and the uppermost 

 lateral bud forms its continuation. 

 Here, also, the branching of each an- 

 nual shoot, apart from its apex, is 

 racemose. 



8. Cohesion and Ad- 

 hesion. It sometimes happens 

 that the originally free edges of 

 parts subsequently grow together ; 

 for instance, the margins of the 

 carpellary leaves to form ovaries. 

 As a rule the rudiments of distinct 

 members become united into one 

 whole by the growth of their com- 

 mon base. For example, a gamo- 

 petalous corolla (see Part IV.) 

 arises in this way, that the whorled 

 leaf -rudiments are raised up by 



FIG. 12. Flower of Petunia : A very 

 young ( x 50) ; B mature (nat. size) ; k 

 the calyx ; V the line along which the 

 calyx has been removed; r the tube, 

 I the lobes or teeth of the corolla. 



