134 BOTANICAL GAZETTE [AUGUST 
face for some distance. It has not thus far been practicable to ascer- 
tain the extreme distance to which either the main or lateral roots 
may extend. At the entrance of an abandoned mine the roots of a 
rather small plant were found exposed at a depth of 3™, and from 
their size at this point, it is probable that they extended 1.5™ or more 
=e farther. Larger specimens doubtless send their 
roots to much greater distances. In any case it 
is seen that the root system spreads widely and 
penetrates deeply into the earth, a disposition well 
adapted to secure what water is available through 
a comparatively wide area when there is a light 
rain, while the longer divisions of the root extend 
—_ to the water. brought by heavier rains that have 
i a reached lower levels. Such an arrangement is all 
ence to plants around the more advantageous in view of the lack of a 
it, on plain north of special storage system, the root as a whole being 
Desert Laboratory. manifestly incapable of holding any considerable 
quantity of water. 
The development of the root has been followed for some months 
by observation of seedlings grown in flower pots and larger recep- 
tacles. Some of the results have been referred to already in the dis- 
cussion of growth of seedlings as affected by water supply. There 
are other facts, however, particularly the behavior of root-hairs and 
their relation to absorption, that require separate consideration. 
Seeds germinated in a Geneva tester, so that the radicles grew 
moist air, gave opportunity to observe the early formation of root 
hairs under these special conditions. As was to be expected from 
what has been observed in other species, they were developed in the 
damp air of the tester while the radicles were still very short, there 
being in some instances numerous root-hairs before the radicle had 
reached a length of 3™™. In other cases it had grown to the length 
of 1°™, more or less, before any were produced. In some cases they 
were close to the root tip, in others farther back, all on one side of the 
tadicle, or projecting from all sides; in short here, where conditions 
were far more nearly uniform than often happens, there was such 
variety of habit as to render it extremely difficult to ascertain the 
factors actually determining the outgrowth of epidermal cells into 
root-hairs. 
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ot I 
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