(i9) 
two halves are constricted asunder into two complete individuals, 
each perfect in form and function. Another mode of reproduc¬ 
tion consists in a gradual elongation of the organism, as already 
described, hut to a greater extent, after which appear dark bodies 
within the living-matter—the so-called spores—and, these having 
reached a relatively large size, the investing membrane of the par¬ 
ent-plant ruptures, and the spores are scattered as new individu¬ 
als. each retaining about it a portion of the protoplasm which 
surrounded it while yet a part of the parent. The reproduction of 
these bacteria is very rapid, when the environment is favorable, 
and, for many varieties, a half-hour suiliccs. Of late years, these 
minute organisms have been found to be the causative agents of 
many dire diseases, the rapid progress of which is more clearlv 
understood when we observe the wonderful activity of reproduc¬ 
tion among certain classes of bacteria. 
Now, let us turn our attention to the more complicated system 
of development found in tlie majority of “phaenogamous,” or 
flowering, plants, which likewise take their origin from the sin¬ 
gle cell or unit of protoplasm. To make the process more intel¬ 
ligible, I present a diagram recalling to your minds the essential 
parts of a flower—sepals, petals, stamens, pistils.* The pistils, as 
indeed, all the parts of the flower, arc merely modified leaves.f 
In each of the pistils, along the line of union of the margins of the 
original leaf, appear a series of outgrowths, known as ovules, 
the portion first appearing being termed the nucleus or body of 
the ovule. From the base or attached portion of the nucleus, 
there grow out two coats about the nucleus, gradually enclosing 
it, there remaining, however, an opening in this envelope termed 
the foramen, which is found just over the apex of the nucleus. 
When complete, then, the ovule consists of a nucleus and (usu¬ 
ally) two coats, which latter present an orifice over the apex of 
the nucleus. A cavitv (the embryo-sac) now forms within the 
nucleus, and, from some portion of the protoplasm lining it, a 
single protoplasmic cell, of globular form, is thrown off, termed 
the embrvonal vesicle, and this rises to tlie apical portion of the 
s ic. The ovule is now mature, and fertilization is brought about 
•Fig. 6. t Fig. 7. 
