22 STEMS [CH. 



plants, circular, or triangular. Such stems may also be 

 hollow, or solid, and all these characters may differ for the 

 nodes and internodes respectively e.g. the solid nodes of 

 Grasses as contrasted with their cylindrical hollow inter- 

 nodes ; the tumid, viscid, hairy nodes of certain Caryo- 

 phyllaceae, as contrasted with their smooth internodes, 

 and so on. 



In the case of trees, descriptive botany takes note of 

 facts similar to the above so far as the young twigs of the 

 current year are concerned, because these are practically 

 herbaceous stems, but the older parts, and especially the 

 trunk, have in the course of years obtained other coverings 

 than those found on herbaceous parts, and the peculiarities 

 of the periderm and bark have to be described. (See 

 Bark 1 .) 



The above remarks apply to the ordinary stems, ac- 

 cepted as such by any observer. Before passing to the 

 consideration of the various kinds of stem which depart 

 more or less from the type, it will be useful to pay some 

 regard to branches of various kinds, also as observed in 

 ordinary plants. 



In all the usual cases, as in our common trees and 

 shrubs, Ash, Elm, Lilac, &c., it is obvious that the ordi- 

 nary leafy branches (foliage branches) simply repeat the 

 peculiarities of the principal stem from which they are 

 outgrowths. We shall see later that there are certain 

 generalisations to be made as regards branching, but for 

 the moment the point is that the ordinary branch essen- 

 tially repeats the structure of the stem : like the latter it 

 ends in a bud, and has its own lateral outgrowths leaves, 

 other branches, &c. and presents similar characters of 

 surface, section, and so on. 



1 Vol. i. pp. 9499. 



