4 OUTLINE OF STRUCTURAL BOTANY 
It is to such works that the student should resort according to 
the degree to which he would carry his study in order that his 
acquaintance with the vegetable world may become an intimate one 
of greatest interest. 
ORGANS OF VEGETATION 
The organs of vegetation consist of the root, the stem and the 
leaves, with those modifications of leaves consisting of the organs 
destined to reproduce the species, the spore in non-flowering plants 
and the flower and fruit of flowering plants. 
THE ROOT 
The root is that part of the plant usually growing downward, 
whose office it is, especially, to absorb from its surrounding medium, 
most commonly the soil, the moisture and some other materials 
. Fic. 1 
from which the plant derives certain elements of its nourishment. 
The root also, in a great majority of cases, serves to fix the plant 
in a position favorable to its existence and growth. It differs from 
the stem in not bearing leaves. 
Some plants, notably many species of the orchid group in tropical 
and semi-tropical climates and some trees, as for example the man- 
grove, are supplied with aerial roots. Some of these roots growing 
in the open air cling to the branches of trees, while other aerial 
roots hang as long, more or less fleshy, pendants or cords exposed 
to the winds. Other aerial roots, arising irregularly in the course 
of the stem, as for example, those from. the stem of the ivy (Fig. 2); 
and which have for their purpose, in general, the support of weak 
climbing stems, are known as adventitous roots. Such roots grow- 
