56 LATICIFEROUS VESSELS. 
phloém of Dicotyledons, and also in the fibro-vascular bundles 
of some Monocotyledons, and elsewhere. If the partition walls 
between the component cells are not really perforated, but only 
thickened in a sieve-like mannef, the name of sieve, lattice, 
or clathrate, is applied to the component cells. 
g. Laticiferous Vessels.—These constitute the Milk-vessels of 
the old authors. They consist usually of long-branched tubes 
lying in no definite position with regard to the other tissues (figs. 
117 and 118), and anastomosing or uniting freely with one 
another like the veins of animals, from which peculiarity they 
may be at once distinguished from the other vessels of plants. 
When first formed these vessels are exceedingly minute and 
their walls are very thin; they become, however, large and 
Fig. 119. 
Fia. 117. Fie. 118. 
Figs. 117, 118. Laticiferous vessels. 
——Fig. 119. Laticiferous vessel 
from Luphorbia splendens : the latex 
contains starch granules of a pecu- 
liar form, After Thomé. 
thick-sided as they increase in age, but even then rarely pre- 
sent any pits or spiral deposits in their interior, as is the 
case in the thickened cells and vessels already described. A 
common size is the ;4,; of an inch in diameter. They derive 
their name from containing a fluid called latex, which when 
exposed to the air becomes milky, and is either white, as in the 
Dandelion, Spurge, Opium Poppy, Indiarubber, Lettuce, and 
’ many other plants ; or coloured, as is well seen in the Celandine, 
where it is yellow; or it may be of other colours. The latex ~ 
has a number of granules or globules floating in it, which are 
composed of caoutchouc or analogous gum-resinous matters, &c., 
and occasionally mixed with them may be observed peculiar- 
shaped starch granules (page 32), as in Euphorbia splendens 
