. GROWTH BY TERMINAL BUDS. 99 
for here we observe extensive swellings produced, which show 
the increase in the diameter of the stem after the twiner has 
encircled it. Such a comparison shows, in a very striking and 
conclusive manner, the characteristic peculiarities of the growth 
of exogenous and endogenous stems. 
Growth by Terminal Buds.—In Palms (fig. 199, 1), and most 
commonly in other Monocotyledons, there are no branches, 
the stems of such plants having no power of forming lateral 
buds, from which branches can alone be produced (see page 
106). These plants, which frequently rise to the height of 
150 feet or more, therefore grow simply by the development 
of a terminal bud, which when it unfolds crowns the summit 
with a tuft of leaves, which are commonly of great size. 
Monocotyledonous stems are consequently exposed throughout 
their whole length to, as far as 
possible, the same influeces as 
regards their increase in dia- 
meter, and we find accordingly, 
that, as a rule, such stems are 
almost uniformly cylindrical 
from below upwards, being of 
the same diameter throughout 
(fig. 199, 1), instead of conical, 
as in trees of exogenous growth. 
In such plants, therefore, the 
destruction of the terminal bud 
necessarily leads to their death, 
as they are then deprived of all 
further mode of increase. In 
some monocotyledonous trees, 
however, more than one bud is 
developed ; thus in the Doum 
Palm of Egypt two buds are 
formed, sothatthestemisforked _ 
above (fig. 200); each branch 
again develops two other buds Fig. 200, The Doum Palm of Egypt 
at its apex in like manner, and (Hyphene pete J, showing forked 
: : : stem and branches. 
this mode of growth is continued 
with the successive branches, which are therefore also forked 
(false dichotomy). In other Monocotyledons we have lateral 
buds formed as in those of Dicotyledons; this is the case 
in the Asparagus, the Screw Pine (fig. 199, 2), and the Dra- 
ceenas (fig. 196); and as the lower part of such stems receives 
more fibro-vascular bundles than the upper, they are necessarily 
larger in their diameter at their base, and thus these stems are 
conical or taper upwards like those of Dicotyledons. 
Anomalous Structure of Monocotyledonous Stems.—Some 
monocotyledonous stems present an anomalous structure ; 
thus, in most Grasses the stem is hollow (fig. 201, «), except 
H 2 
Fie. 200. 
y Bai 
