154 PHOTO-MICROGRAPHS. 
discharges, or any other cause, is especially lia- 
ble to fall a victim to those epidemic diseases 
which are supposed to be of parasitic origin. 
Many parasitic fungi will only grow upon a par. 
ticular kind of plant, or even upon a special vari- 
ety produced by cultivation. Thus, a hardy native 
rose may go unscathed, while a cultivated variety 
in its immediate vicinity suffers from the attacks 
of mildew. 
Those who desire fuller information in regard to 
the microscopic fungi are referred to the Micro- 
eraphic Dictionary, which gives all the informa- 
tion which amateur microscopists are likely to 
require. 
EpirHetium Cexiis. (Puate IV. Fics. 1 anp 2.) 
Tf a little drop of saliva from the mouth be ex- 
amined under the microscope, it will be found to 
contain numerous flat cells, of somewhat irregular 
form, which have been shed from the surface of the 
mucous membrane lining the cavity. By the use 
of staining reagents, it will be seen that these 
cells have a nucleus—seen in the centre of the 
cell in the figure —and a nucleolus. The deeply- 
stained spherical and rod-shaped bodies seen upon 
the surface of the epithelium cell in Fig. 1 are 
Bacteria. 
Epithelium cells of different forms, and some- 
what differently arranged, make up the super- 
ficial layer of all membranes lining the cavities 
of animal bodies; and the cuticle or epidermis 
