54 GROUPS OF TISSUES, OR TISSUE SYSTEMS 
(e) Root hairs may be studied in cross- or longitudinal-sec- 
tions of the young roots of seedlings that have been germinated 
between damp cloth or paper, or in moist air. By adding a 
rather strong sugar, or potassium nitrate solution the cyto- 
plasm may be drawn away from the walls sufficiently (plas- 
molyzed) to become visible. 
(f) The leaves of various grasses (e.g. Panicum capillare) 
will show simple one-celled hairs. The petunia stem possesses 
unbranched hairs, consisting of rows of cells. Many will be 
found to terminate in glandular cells. Hairs of these same types 
may be found on tobacco, various species of Silene and very 
many other plants. 
(g) The stems and leaves of various crucifers (e.g. Erysi- 
mum, Arabis, Bursa), show bifid hairs. Stellate and peltate 
hairs are shown best on the leaves of species of Elaeagnus and 
Shepherdia. 
(h) The hairs of the common mullein (Verbascum thapsus) 
may be studied as examples of greatly branched hairs. 
(t) Cross-sections of the leaf or stem of nettle (Urtica and 
related genera) will show the peculiar stinging hairs. Under 
high power note the terminal knob which breaks off as the hair 
penetrates the skin, thus permitting the distended base of the 
turgid hair to contract and discharge the poisonous contents 
into the skin. 
77. The Conducting System. In most of the lower 
algae and in the fungi, the plant body consists of separate 
branching filaments, which are in some cases woven 
together into a more or less firm body. These filaments 
are about alike, and are mostly not differentiated into 
conducting and other filaments. In some of the more 
massive algae, however, as in the larger kelps (Laminaria, 
etc.), or rock weeds (Fucus, etc.), the internal cells. 
are much more elongated, and seem to conduct the 
elaborated food stuffs from one part of the plant to the 
other, true sieve tissue sometimes being present. A 
system of water-conducting tissue is not evolved until 
the Mosses are reached. Here the center of the stem is 
occupied by elongated cells, that serve probably in part 
