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fore be considered as a tissue-system. A portion of the bundle 
always remains for a time in a condition capable of further 
development, constituting the Cambium , which frequently 
divides the bundles into two distinct portions, called by Nageli 
the Phloem and the Xylem portions of the bundle ; the former 
consisting of succulent, generally thin-walled cells, the latter 
having mostly a strong tendency to thicken its cell-walls. It is 
not, however, necessary for the fibro-vascular bundle to contain 
pure woody tissue. Spiral vessels occur always in the veins of 
the leaves and in the medullary sheath of the stem of Exogens. 
The fibro-vascular bundles are extremely well seen in a trans- 
verse section of a leaf-stalk of any exogenous plant ; from the 
petiole they ramify into the blade of the leaf, forming the veins 
or nerves. 
3. The Fundamental Tissue is the term given by Sachs to 
those masses of tissue of a plant or of an organ which still remain 
in their original condition after the differentiation of the 
epidermal tissue and the fibro-vascular bundles. It may consist 
of various descriptions of tissue, but is always to a large extent 
parenchymatous. In the leaves of Ferns and Flowering Plants the 
fundamental tissue forms by far the larger portion, constituting 
the “ mesophyll.” 
4. Laticiferous Vessels and Intercellular Spaces may occur 
in any of the three systems of tissue now described, and some- 
times pass into them by insensible gradations. The true Latici- 
ferous Vessels are canals filled with milky sap resulting from 
the coalescence of rows of cells, and lying in the phloem portion 
of the fibro-vascular bundles. They occur abundantly in many 
orders of plants, as the Papaveracese, Convolvulacse, Cichoriacese, 
Euphorbiacese, &c. The Intercellular Passages result from the 
separation from one another of rows of cells, and are also 
frequently filled with a milky, oily, or resinous fluid, as in 
Umbelliferse and Coniferse. 
The different kinds of tissue now described are to be met 
with only in the more or less mature parts of plants. The 
parts which are actually in a state of growth, as the ends of 
shoots, leaves, and roots, consist of a uniform tissue, the cells of 
which are all capable of division, rich in protoplasm, with thin 
and smooth walls, and containing no coarse granules, to which 
the term Primary Meristem has been given. From this 
the Epidermal Tissue and Fibro-vascular Bundles are differen- 
tiated as the organ develops, the portion which undergoes 
comparatively little change being distinguished as the Funda- 
mental Tissue. The terminal portion of an organ with perma- 
nent apical growth, which consists entirely of primary 
meristem, is termed the Punctum Vegetationis ; or when, as is 
sometimes the case, it projects as a conical elongation, the 
