4 BOTANY. 
Soda, Lime, Alumina, Magnesia, Silica, and Iron ; more rarely ‘lodine, 
Chlorine, Copper, Bromine, and Manganese. These will be subsequently. 
referred to more at length. Starch is included in the cells of all plants at 
some period of their existence, and forms one of the most important distine- 
tive characters between the animal and vegetable tissues. Crystals also, or 
Raphides of various shapes and characters are found in the interior of cells, 
either lying loose or suspended from the walls. Sometimes there will be a 
single large crystal in a cell, and again several may be inclosed together. 
They abound in certain plants, as Cacti, to such an extent, as to exceed in 
weight the other constituents of the tissue. The raphides are all formed by 
the action of organic acids, as phosphoric, oxalic, &c. | 
Jelly is another occasional element of cells. This is hard and horny 
when dry, slowly soluble in water, and unacted on by iodine. It sometimes ~ 
fills particular cells, as in the stems of some Cacti. It is to this substance 
that carrageen moss and other plants owe their gelatinous properties. 
Chlorophylle, the green coloring matter of plants, and Chromule, the 
coloring matter not green, are additional contents of cells. 
Various and quite conflicting opinions have been propounded by different 
eminent vegetable physiologists as to the development (Cytogenesis) and 
functions of cells. Perhaps the more generally received opinion is, that in 
the blastema, or primordial matter, the nucleus, which is itself a minute cell, 
is first formed, and exerting a directing influence upon the inclosing matter, 
causes it to assume a cell-shape. With the absorption of new matter from 
the blastema the nucleoli increase in size and finally separate, each one 
forming around itself new cells, which, enlarging, burst the original cell. 
The new cells contain nucleated nuclei, by means of which the same 
operation is repeated, the increase taking place in a determinate direction. 
This constitutes the endogenous theory of cell development. The exogenous 
theory supposes an influence to be exerted by a cell on the surrounding 
matter, resulting in the addition or aggregation of new matter. This view 
does not require the existence of a nucleus. According to others, again, the 
old cell becomes separated by a constriction, or a projecting partition, into 
two cells, each of which may or may not include a nucleus. This is the 
merismatic or fissiparous theory. Many attribute to electric currents, 
produced by the various chemical actions, the influences which cause the 
different ceil phenomena. The development of cells sometimes takes place 
with extraordinary rapidity, especially in the Fungi. Thus, in Bovista 
gigantea, they have been supposed to be produced at the rate of sixty-six 
millions in a minute. 
2. VAScuLAR TISSUE. 
VascuLar Tissuz, or ANGIENCHYMA, consists of tubes whose length 
greatly exceeds their breadth. They may be formed of membrane only, 
or of membrane variously modified. Woody fibre, or ligneous tissue 
(Pleurenchyma), consists of tubes or elongated cells, of a fusiform or 
spindle-shape, with the walls greatly thickened by sclerogenous deposits. 
4 
