THE STEM. 25 
the principle of the hollow column, as in the culms of grasses. 
Overground stems may serve as receptacles for reserve materials, 
and in this case the internodes may either be of considerable 
length, as in the trunks of trees, which during winter contain 
large quantities of starch, &c., or they may be much shortened. 
A familiar example of such a condensed stem is the cabbage, in 
which plant, however, nutriment is stored not only in the short- 
ened stem, but also in the bases of the leaf-stalks. 
Overground stems which are not erect may have a greater or 
less tendency towards the horizontal position, or, on the other 
hand, they may compensate their want of strength by climbing. 
In the former case, the first approach to a horizontal position is 
found in ascending stems which grow obliquely upwards. When 
a stem commences by being erect or ascending, and then turns 
down and runs along the ground, it is said to be recumbent. The 
opposite of this is seen in decumbent stems, which first run along 
the ground and then become ascending. Lastly, the horizontal 
direction may be taken from the first, when the term procumbent 
or prostrate is employed. Such a stem is creeping if it gives rise 
to adventitious roots at its nodes. A few terms that are applied 
to branches which serve for the multiplication of plants may here 
receive mention. Suckers are ascending branches of subterranean 
stems. The green shoots commonly growing up from near the 
base of standard roses are of this nature, and so are the new 
“canes”? developed each year from raspberry bushes. Stolons 
are prostrate or reclined branches which take root at the end, 
where a new shoot then grows upwards, and a fresh plant is thus 
formed. Slender elongated stolons are runners, as in strawberry, 
while short thick ones are offsets, as in house-leek. Short suckers 
are also called offsets. 
Climbing Stems.—In many climbing forms the main stem 
itself winds round and round a support. Such twining stems 
form either right-handed or left-handed spirals. In the former 
case, which is the commoner, and of which scarlet runner and 
convolvulus are examples, the coils ascend from left to right, as 
in a corkscrew. The exact opposite is the case in the hop and 
certain other stems, which form left-handed spirals. Another 
large class may be called tendril-climbers, since they possess irri- 
table clasping organs in the form of tendrils, which are thin, 
elongated, stem-like structures, capable of turning round and 
round a support. Tendrils may be either modified parts of the 
stem, or flower-stalks, or parts of leaves. In the cucumber 
and vegetable marrow the tendrils are branches, while in the 
vine they take origin opposite the leaves (p. 27). The same thing 
is true of the Virginian creeper, where, in addition, there may be 
