STEMS, LEAVES, AND BUDS. 
51 
Delineations of the internal structure of soUie Cactacece are 
represented in the Sel. Icon. Anat. Bot. part ii., tab. 3. The 
woody bundles in the stem of Epiphyllum phyllanthus are 
separated from each other at the points, where the stem has 
still its round form, and each bundle is surrounded by its 
alburnum, upon which follow the liber, separated in the same 
manner, and surrounded as usual by the bark, and opposite 
the woody bundles (see fig. 1). The alburnum consists of 
very tender small cells of parenchyma, the liber of very thick 
walls, or finely punctated liber vessels, rarely with partitions, 
but they are found in some (fig. 2) ; ramified, frequently 
reticulated spiroids are seen in the flat part of the stem, 
which are inclined towards the spot where the tufts of thorns 
are seated (fig. 3). The leaf, therefore, seems really to be 
transposed into the wings of the stem, for such a separation 
of vessels is not found in the stem of the Dicotyledons, nor 
in the stem of the same plant where it is round. 
The internal structure of Opuntia vulgaris is likewise 
represented. A similar division of the spiroids towards the 
thorn tufts is likewise seen here, as in the flat part of the 
trunk of Epiphyllum phyllanthus (fig. 4). The joints of the 
stem or branches of the Opuntim are perfectly compressed, and 
that in such a manner, that the woody bundles are situated 
remotely from each other (fig. 5). Where the stem of the 
Opuntice is round, there it has the internal structure of 
the Cactaceoe in general, a thick bark, and woody bundles 
separated from each other (figs. 6, 7). The spiral vessels 
and spiroids also ramify towards the tufts of thorns in the 
Cereus flahelliformis (fig. 9) ; the fluid distension is, however, 
principally owing to the enlargement of the bark, which is 
much thicker than the pith (fig. 9). 
Decaisne, in his Mem. sur le Developement du Pollen, de 
r Ovule, et sur le Structure des Tiges de Gui, Bruxell., 1840 
(Exte. du t. xiii. de FAcadem. E. de Bruxell.), has communi- 
cated some observations on the Stem of the Mistletoe {Viscum 
album). He first alludes to the remarks made by De Candolle, 
Kaiser, and Dutrochet, respecting it. Dutrochet asserts, that 
each joint of the stem grows independent of another ; that 
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