Lf i 4 he, i pet © Aen 2 2 " 4 4 i 
Ne ~: ' > . a8 - 4 tad , j - - 
* 4 as , s i: iY qe “fy od ’ \ he 
LLM g es wr pal vay ya’ wy. \ . ‘ A 
SAE eh: FN A 
Part ONS yey oa) PRE Tse we has Me ee alla hs Sah ES PS , oti * eng 
‘The Construction of the Plant out of Cells. 69» 
~ elements themselves that are present, it is very often possible to recog- 
nise the species from a small fragment of the plant. Only in com- 
paratively few cases are the plants adapted at once 
for microscopical examination. When they are not 
so adapted, they must be dissected into small trans- 
parent pieces; and the direction in which the 
section has been made must also be noted. In 
order to examine, for example, the structure of a 
branch, preparations must be made, taken from it 
principally in the following three ways (Fig. 96) : 
in the transverse section a 6 at right angles to the 
axis of growth we, the longitudinal section cd 
through the axis, and the fazgentzal section ef 
parallel to it.’ Sections in-other directions, as the 
oblique gh, are only occasionally needed. In 
certain cases it is also requisite, in order to make 
the preparation transparent or decompose it into 
its separate elements, to macerate it, especially 
when it is desired to determine the form and con- 
nection of the individual cells. We have here no 
space to enter into a detailed account of the ap- n: 
plication of the microscope to botanical investiga- Fi. 96.—Diagram re- 
: E ; presenting the various 
tion, and can only refer to the works of Dippel, sections of a stem. 
Harting, Nageli and Schwendener, and Schacht. 
i} 
' 
1 
1 
| 
i) 
1 
! 
! 
1 
if 
| 
st 
f 
CHAPTER, 1V* 
THE EXTERNAL FORM OF PLANTS. 
In the plants of lowest organisation, Alge, Fungi, and 
Lichens, the contrast which is so manifest in those more — 
highly developed between an axis (stem and root) and the . 
lateral organs (leaves), is altogether wanting. With reference 
to this point, the vegetable kingdom is therefore divided 
primarily into plants without an axis or Zhallophytes, and 
plants with an axis or Cormophytes, the term thallus being 
applied to a structure destitute of leaves. _ 
‘The external differentiation of the parts in cormo- 
phytes can be very well seen in a germinating pea. If the 
