96 ORIGIN AND GROWTH OF THE FIBRO-VASCULAR BUNDLES, 
in fig. 193, a, b, c, d, the last-formed bundles being the most 
internal, and gradually pushing towards the circumference those 
which had previously been developed. Hence the origin of 
the name endogenous or inside growers, applied to these stems. 
The researches of Mohl first showed that the above mode of 
growth was not correct, but that the fcllowing is that which 
really takes place:—the fibro-vascular bundles have their 
origin in the punctum vegetationis of the stem, and are fully 
developed with its growth upwards and outwards into the leaves, 
and downwards and outwards towards the circumference of the 
stem. In other words, to render it more simple, the bundles 
may be traced to the leaves, from which organs they are at first 
directed towards the interior of the stem (jig. 194, a, b, ¢, d), 
along which they descend generally for some distance, and then 
gradually curve outwards again and terminate close to the 
circumference, where they anastomose and thus form a net- 
work with the ends of other bundles. When we make a vertical 
section therefore of an endogenous stem, we find these fibro- 
vascular bundles intersecting each other in various ways as shown 
in fig. 195. 
When the fibro-vascular bundles thus pass from the stem into 
the leaves at their upper ends, they are termed common bundles, 
namely, common to both leaf and stem—those portions coming 
from, or continuous with, the leaves, being called leaf-traces. 
The fibro-vascular bundles in their course down the stem 
generally become more attenuated, which circumstance arises 
from certain differences which take place in their structure as 
they descend. Thus when they first originate they consist, as 
we have seen (see page 77), of spiral, pitted, and other vessels, 
mixed with parenchymatous and woody tissues (fig. 192, B, 
b, c,d). In their descent they gradually lose their spiral and 
other vessels, so that when they terminate close to the circum- 
ference they consist chiefly of a net-work of liber-cells bound 
together and covered by a more or less developed cortical 
parenchyma. The rind or false bark (fig. 177, b) of endogenous 
stems is thus chiefly formed of the ends of the fibro-vascular 
bundles which originate in the leaves, and hence we see the 
principal reason why this rind cannot be separated, as the bark 
of exogenous stems, from the tissues beneath. 
It follows from the mode of growth of the fibro-vascular 
bundles, as indicated above, that the term endogenous, commonly 
applied to such stems, is not altogether correct, as the bundles 
are only endogenous for a portion of their course, terminating 
as they do ultimately close to the circumference. On this account 
the name endogenous has been generally discarded of late years 
by botanists, who use instead that of monocotyledonous, aterm, as 
already noticed (page 78), which is derived from the fact that the 
embryo of plants which possess such stems has but one cotyledon. 
In this volume we have employed both terms, and so long as that 
