STRUCTURAL BOTANY. 87 



of the plijllotaxj of the future stem, or branch, and the 

 various modes of praefoliation are denominated the tri- 

 quetrous, decussate, quincuncial, etc. The terms tri- 

 quetrous and quincuncial denote in praefoliation the same 

 arrangement of the parts as in sestivation, of which Ave 

 have treated in the chapter on the flower. 



166, Before we conclude this chapter on Phyllotaxy, 

 we must treat of huds in general. 



Leaf-huds contain the rudiments of a leafj stem or 

 branch, v^\i\\q flower-huds enclose the same elements trans- 

 foiTned, and destined to perform, directly or indirectly, the 

 reproductive functions of the plant. Leaf-huds appear in 

 the form of a tender-pointed cone, covered with scales. 

 These buds regularly develop in the leaf-axils, and are 

 then called axillary buds. Leaf-axil is the angle formed 

 by the leaf with the supporting axis (stem or branch) on 

 the upper side. 



Buds become leafy branches, just as the plumule became 

 a stem. From the axils of the leaves along the branches 

 we see other buds making their appearance, which give 

 rise to branches in their turn. 



Some plants do not branch, but consist of a simple shaft. 

 Plants of this sort, as palms, grow by the continued evo- 

 lution of a bud, which crowns the summit of the stem, the 

 terminal lud. But terminal buds occur in branching 

 plants also, as on all the stems or shoots of Acer, ^scu- 

 lus, Carya, etc. (PI. I., 3i, 35.) In growing, they only 

 prolong the shoot, or stem. Yet down the sides of the 

 same shoots other buds are produced, just over the scars, 

 left by the leaves which fell the autumn previous — axillary 

 buds. 



A curious sort of buds are those known as adventitious 

 or accidental. They are neither axillary, nor terminal, but 



