24 THE FLOWERING PLAN’. 
many climbing and creeping plants. On the other hand, the 
internodes may be so extremely short as to make the stem a 
scarcely recognisable stump, the leaves being at the same time 
crowded into a tuft or rosette. Good examples are daisy, dande- 
lion, and house-leek. Such an abbreviated stem is sometimes 
termed a root-stock, while the leaves growing from it are radical, 
the old (but erroneous) idea being that they grew from the root. 
It may also happen, as in the buttercup, that the internodes are 
very short in the lower part of the stem only. The leaves borne 
by that part are then also called radical. 
The thickness of a stem is dependent on other conditions besides 
the length of the internodes. Perennial gymnosperms and dicoty- 
ledons (rarely monocotyledons) undergo an annual increase in 
thickness, and many stems and branches, particularly underground 
ones, are thickened in connection with the storage of reserve 
materials. 
The chief factor determining the general shape of a stem 
system is the nature of the branching. ‘Ibis is monopodial, as in 
the case of the root, and two kinds may be distinguished: (1.) 
Racemose, where, as in most cases, the main axis continues to 
grow, and is larger and longer than their branches, which, in their 
turn, bear a similar relation to its subordinates. The pyramidal 
outline of many trees, e.g., firs, is due to this cause. (2.) Cymose, 
where the main and other axes cease growing after a time, and 
are outstripped by their branches. This may result in false 
dichotomy, 7.e., apparent forking, as in the mistletoe; or a pseud- 
axis or sympodium may be formed, where the direction of an axis 
is continued by one of its branches, which after.a certain time is 
supplanted by one of its branches, and so on (cf. p. 48). The 
name pseud-axis is given because, at first sight, we have to deal 
with a case of racemose branching. Examples are found in the 
twigs of elm and beech. The main branching of these trees is, 
however, racemose. Special branch systems or inflorescences are 
often developed, upon which the flowers are borne. These will be 
dealt with later on in connection with the flower. / 
The last important point which determines the shape of the 
stem is its direction, whether vertical, horizontal, or otherwise. 
In giving a brief account of various stems, it will be convenient 
first to speak of aérial forms and then to proceed to subterranean 
ones. 
Aérial Stems.—As already mentioned, the typical overground 
main stem is erect and self-supporting. This requires a consider- 
able amount of strength, which may be gained by size and solidity, 
as in tree-trunks, or where there is comparatively little substance 
this may be disposed in the most advantageous mannet, 7.e., on 
