ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
61 
which bound intercellular spaces ; (6) collenchyme resulting from 
secondary metamorphosis which has taken place at a late period (meta- 
collenchyme ; (7) temporary collenchyme or proto-sclerenchyme. 
Collenchyme-tissue is always distinguished from bast-cells by being 
composed of living cells. It seldom contains more than a small quan- 
tity of chlorophyll ; but, whether in a young or mature condition, its 
cells are always filled with water, and its primary function is to serve as a 
store-house for water, which is also always contained in the thickenings. 
At an early period, however, it always acquires its secondary function 
as a mechanical supporting- tissue ; and this it performs not only while 
the organs are increasing in size, but also when they have passed over 
into its permanent condition. 
Nutrient Layer in the Testa.* — Herr J. Holfert has investigated 
the structure of the layer which is almost always found beneath the 
sclerenchymatous layer in the testa of seeds. Although in the ripe seed 
this zone has very commonly entirely disappeared, in the unripe seed it 
consists of cells of ordinary structure, containing abundance of water, 
starch, and even of chlorophyll-grains. It is a transitory storing-tissue, 
and consists of parenchymatous cells, the contents of which are used up, 
during the process of ripening, in secondary cell-wall thickenings and 
other portions of the tissue of the testa. It may occur in one layer or 
two, separated by sclerenchyme. 
The author classifies the various forms of this tissue under three 
types, of which the first is by far the most common, viz. : — (1) There are 
one or more nutrient layers and one or more sclerenchymatous or collen- 
chymatous or thick-walled layers with secondary thickenings ; (2) one 
nutrient layer, and no layers with secondary thickenings ; (3) the 
nutrient layer is replaced by a permanent layer of parenchyme ; there 
are no layers with secondary thickenings. This nutrient tissue is 
usually developed from one or more rows of cells, not to be dis- 
tinguished from the rest, in the integument of the unimpregnated ovule. 
The number of rows of cells almost always increases, and sometimes the 
tissue is entirely formed, after impregnation. A very large number of 
special cases are described belonging to a great many different natural 
orders. 
Foliar Fibrovascular System.j — By this term M. 0. Lignier under- 
stands all the bundles which descend from a leaf, whatever their number 
or distribution, as well as those which penetrate the limb and the petiole 
of the leaf, and those which descend into the stem and constitute the leaf- 
trace. In the simplest case (Conifers and some Angiosperms) this system 
is composed simply of a single bundle, situated in the plane of symmetry 
of the leaf; but it is usually much more complicated. One mode of 
complication consists in a lateral extension, and also often a longi- 
tudinal breaking-up of the conducting tissues. The system may, when 
more complicated, consist of one or more principal bundles distributed 
over a more or less open convex arc ; the broadening of these produces 
secondary (supernumerary) bundles, which again may be changed from 
* Flora, lxxiii. (1890) pp. 279-313 (2 pis.). 
t Bull. Soc. Linn. Normandie, 1888-9 (1890) pp. 81-92. Cf. this Journal, 1888, 
p. 985. 
