STEMS, LEAVES, AND BUDS. 
37 
1st, The vascular bundles of the stem extend themselves, in 
their development, towards the upper part of the stem, with- 
out multiplying themselves ; and by this mode of growth, 
produce additions to the ^oint or the end acrogenous growth 
(vegetatio terminalis), as is seen in the Cycadacece and 
Ferns. 2d, The vascular bundles of the stem have only a 
certain length, and the stem is enlarged and lengthened by 
new vascular bundles, which are added to those already 
existing, and attach themselves to those on the outside and 
over them ; this produces the endogenous growth (vegetatio 
peripherica). Finally, A third kind, which is perfectly dis- 
tinct from the two preceding kinds, and which is distinguished 
by the circumstance, that the vascular bundles do hot only 
extend themselves towards the upper end, but at the same 
time towards the outside, which occasions the formation of a 
central and peripheral system of vascular bundles. This kind 
of vegetation is exogenous (vegetatio peripherico terminalis), 
IX. Anatomical character of the Cambium Layer. — The 
author here particularly alludes to the growing together of 
the cells ; he believes, that this may be best observed in the 
lower plants, as in the Algoe ; and by researches on the 
subject, combined with other circumstances, he has come to 
the conclusion, that the increase of the cellular tissue is prin- 
cipally effected by division. 
Every attention is due to the researches of the author, but, 
in my opinion, he has overlooked many things. It is, in the 
first place, indispensably requisite, to distinguish the different 
kinds of stems, if we wish to obtain a correct view of the 
structure of the stem. In relation to the researches of the 
author, two kinds may be mentioned : — First, The Genuine 
Stem (caulis genuinus), which continues to grow by means of 
buds, so that the buds extend themselves in length, and the 
leaves being in the course of development pushed asunder, 
the lowest leaves, or even the covering leaves (tegmenta) of 
the buds fill their places. This kind of stem is peculiar to all 
Dicotyledons, if we except the stemless plants (PI. acaules), 
to the grasses, the Smilacece, and some of the palms. Most of 
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