86 
ORGANOGRAPHY. 
BOOK I. 
and upon this, and my own observations, the following account 
of them is founded. 
Laticiferous tissue ( Vital vessels, Vasa opopJwra) consists of 
branched anastomosing tubes, lying in no definite position with 
regard to other tissue, large and thick-sided when old, but so 
capillary and thin when young as hardly to be visible. The 
sides are not parallel as in other vessels, but often contracted 
and expanded at intervals, so that they may be described as 
partially closed up by strictures here and there : they are said 
to have a power of contraction, but there are no valves or dis- 
sepiments in their interior. The larger trunks Schultz calls 
vasa expansa, and the fine ramifications vasa contracta. 
This kind of tissue has generally an undulatory direction 
(Plate II., fig. 19.). In their interior there is a quantity of 
granular matter^ which sometimes fills them wholly, and 
sometimes is separated by empty spaces. Their average size 
is of an inch. Their sides, although they thicken by 
the successive deposit of new matter, never offer any marks, 
or pits, or other interruptions of continuity. 
It is obvious from these characters that cinenchyma is 
quite different from every other form of tissue. Its constant, 
irregular branching and anastomosing would alone distin- 
guish it. 
As such vessels lie in no definite direction with respect to 
the rest of the tissue, they have been generally overlooked, and 
are often very difficult to find, although always present in 
the greater part of flowering plants. M. Schultz recommends 
maceration for five or six days, as affording a ready means of 
separating them from the surrounding tissue. It is, however, 
easy to find them in the liber of the Fig, in the roots of 
Dandelion, Scorzonera, Lettuce, and other milky Cichoraceae, 
or in any of the parts of Chelidonium. 
They are placed in great abundance in the innermost 
layers of the liber, across the Parenchyma of foliaceous organs, 
in the bark of the root, in the pith, and probably in all other 
parts ; but their station seems to vary in different species. 
Sometimes they accompany the spiral vessels, forming a part 
of the bundle of tissue to which those organs belong. From 
the interior parts they proceed by finer and finer ramifications 
