146 
Journal of Mycology 
[Vol. 10 
the great majority of them being microscopic. Reference has 
already been made to such examples as the microscopic Bacteria 
and Yeasts; correspondingly simple unicellular animals are the 
Amoebae, the Infusoria, and in fact all those organisms belonging 
to the group sometimes called the Pro-tis’-ta. But most of our 
well known common plants (and animals) consist of more than 
one cell; they are multicellular organisms. Yet in their earliest 
stage of development the plants (and animals) consisted of a 
single cell — for the tiny mass of protoplasm, derived from a 
parent mass, is the incipient cell of the individual. The biological 
unit, as the cell may be called, as understood to-day is not a sim¬ 
ple homogeneous mass of matter. On the contrary, it is very 
complex in structure and possesses varied functions; but of these 
phases our knowledge is as yet very incomplete. The branch of 
botany that deals with the cell in its various aspects is called 
Cy-tol’-o-gy, and a large mass of literature touching this subject 
has already appeared. While we can not here enter even into the 
elements of cytology, it is well to remark that the process of 
division of a single cell into two cells is very complicated. In the 
cases best understood, the initial activity is seen in the nucleus. 
This is a dense, well defined, but highly complex portion of the 
protoplasm and ordinarily of easy recognition upon microscopic 
examination. Immediately after the nuclear division processes 
take place — for illustration of which the larger manuals of botany 
must be consulted — the division of the cyf-to-plasm follows — 
this term being used to designate the remaining portion of the 
protoplasm. Simultaneously with the division of the cytoplasm 
or immediately thereafter, a cell-wall, or partition wall of cellu¬ 
lose, is formed which completes the division of the so-called 
mother cell into two daughter cells. Suffice it to add that by 
such repeated cell divisions, the tissue of plants is built up. Nat¬ 
urally the cells in the early stages of development and growth 
are quite uniform; but this homogeneity is retained only in their 
embryonic stage — as this phase has been designated. They take 
on different shapes presently, and respond to the demands of a 
complicated organism by assuming also varied and peculiar func¬ 
tions. 
Continuity of Protoplasm. — When the early plant an¬ 
atomists made sections of leaf, stem and other parts, the con¬ 
spicuous cavities separated and bounded by partition walls re¬ 
ceived their first attention. .These they called cells. But the mod¬ 
ern conception of a cell is very different. It is regarded as the 
living active nearly colorless protoplasm , and this it is which 
secretes or builds up the wall. The wall then is not an essential 
part of a living cell, though in fact being generally developed 
in plant organisms and forming the stable or firm, often dense 
and resistant, plant body. The wall consists of cellulose with 
which (as in all organic matter) are indissolubly united some 
