CELLULAR ANATOMY OF THE ROOT TIP 143 
known to reach a depth of 60 feet. Plants with the Alfalfa type 
of root system are not only drought resistant, but also loosen the 
subsoil, which is thereby put in better condition for those plants 
with roots less able to penetrate a hard subsoil. 
Root Structure 
As the student already knows, plant organs consist of tissues, 
each of which on account of the peculiar structure of its cells is 
especially adapted to do a certain kind of work. 
In roots there are tissues to perform the following 
functions: (1) protection; (2) growth; (3) absorp- 
tion; (4) conduction; and (5) strengthening. Root 
tips show on their surface rather distinct regions, 
which differ in color, texture, or some other feature 
that can be seen without a microscope. Often, but 
not always, the small protective cap, which is the 
actual end of the root, can be identified by its 
brownish color. The smooth whitish zone, which is 
usually a conspicuous region of the tip, is where 
cell multiplication and growth are most prominent. 
Just back of this is the absorptive zone, bearing 
numerous root hairs which are more conspicuous Rie. iey: 
when grown in moist air or moss where there are no _ Tip region 
soil particles to influence their shape. (Fig. 127.) of a root of 
Back of the absorptive region, where protective and Red Clover, 
strengthening tissues are becoming prominent, the Showing root 
root is firmer in texture and darker in color; and ** 
these features become more prominent with age, as is well dem- 
onstrated in shrubs and trees where the older parts of roots are 
woody and covered with thick bark. 
Cellular Anatomy of the Root Tip. — If with the aid of a micro- 
scope a lengthwise section through a root tip is studied, more may 
be learned about the character of the different tissues. (Fig. 128.) 
The root cap now appears as a well defined structure, consisting 
of many cells loosely joined into a covering, which is thickest 
directly over the end of the root. Next to the root cap is the 
zone of cells active in division and constituting meristematic tissue. 
Back of this is the growth zone, in which the chief activity is cell 
enlargement to which the elongation of the root is due. Other 
