186 Mr. A. Henfrey on some Points in the Structure 
There is another point in the strueture of Monocotyledons 
which does not appear to me to be clearly understood. In 
the cortical region are often found fibrous bundles, passing into 
the leaves above, and which, in the cases I have examined, pos- 
sess no vessels, and consequently have the character of liber 
bundles. In Sparganium ramosum they are very numerous and 
of considerable size; they are also found in the Grasses, and 
apparently in all such stems as have the internodial portions 
developed. I cannot find them in bulbs, or in such rhizomes as 
the common Iris; but in the flowering-stem of many such 
plants, ex. gr. the Tulips, Crown Imperial, Tiger Lily, &c., the 
parenchyma gradually changes its character towards the peri- 
phery, and just within the epidermal layers it consists of long 
fibrous cells exactly resembling liber cells. This ring of woody 
cells is very much developed in Tamus communis and Smilax 
aspera (and I believe in most plants belonging to the same orders), 
and has been taken for a layer of wood analogous to that of Di- 
cotyledons ; but this is certainly a misconception, as it is di- 
stinctly defined at its outer border, and does not present the 
slightest trace of a developing or cambium layer. Internally it 
passes insensibly into the central parenchyma of the stem, in 
which lie the true woody bundles having vessels as usual. If 
this has an analogue at all in Dicotyledons, it is the liber ; and 
there are many reasons in favour of such an hypothesis, espe- 
cially if we consider it as identical with the fibres of the cortical 
layer of such stems as Sparganium. 
In conclusion, adverting to the discussions as to the mode of 
increase of the stem of Monocotyledons, it seems to me that 
many writers do not sufficiently consider the peculiar characters 
of this organ. This question must not at all be mixed up with 
that of the formation of new layers of wood in Dicotyledons, 
since in all the usual forms (making exception of such as 
Draccena, Cordyline, &c.) nothing analogous to the second yearns 
layer of wood is ever produced. In bulbs the buds are thrown 
off ; in branching rhizomes they become independent physiolo- 
gically, and the old stem never increases; while in the Palms, 
the bud, though continually developing, merely applies a new 
layer spirally upon the pre-existing portions, so that the new 
growth might be roughly exemplified by a series of hollow cones 
of equal size placed one upon another. Here all growth is ana- 
logous to the upward growth of the terminal bud of a dicotyledon ; 
there is no cambium layer, and no peripherical increase*. The 
* For every year’s development of tlie terminal bud of a dicotyledon we 
find a new layer deposited all over the old wood by the cambium layer, form- 
ing a new annual ring ; in Palms we have merely the terminal shoot with- 
out any analogue of the annual ring. 
