64 GROUPS OF TISSUES, OR TISSUE SYSTEMS 
(lt) Reduced bundles and bundle endings can be studied in 
leaves and petals by placing them in some clearing fluid, e.g. a 
mixture of phenol (carbolic acid), and turpentine after 15 to 20 
minutes’ treatment with 95 per cent alcohol. Mount in the 
same fluid and examine under low and high powers. If these 
objects are previously placed with their cut ends in an aque- 
ous safranin or eosin solution until the colored liquid has 
filled the bundles these are more conspicuous. 
(m) Examine the cut ends of logs and stumps of various kinds, _ 
to distinguish the heart wood and sap wood. That they are 
different in some of their chemical characteristics will be shown 
by their different proneness to decay. 
94. The Supporting System. In many plants the 
supporting and conducting systems are intimately 
connected, the vascular bundles containing not only the 
conducting cells but also an abundance of wood and bast 
fibers. However, at first the stems are often supported 
by other means. Thus, a strong development of 
collenchyma strands under the epidermis is a very com- 
mon occurrence. By the natural turgor and growth 
of the stem, these collenchyma strands are stretched, 
and thus stiffen the stem until the fibrous tissues 
are developed later in connection with the vas- 
cular bundles. In the cortex, bast bundles are fre- 
quently encountered, inde- 
pendent of any _ vascular 
bundles. In the stems of 
Ferns and Fern Allies, large 
OEE et Saat ae tg a bundles of fibrous tissues are 
Boake a i ee scattered here and _ there. 
Closely allied to the support- 
ing system of tissues, in function, are those tissues that 
serve for protection, as for example, the sclerenchyma, 
deposited in various parts of the plant, such as the 
bark, roots, fruits, and seeds. 
