i8 
PHARMACEUTICAL BOTANY 
5 . Lower epidermis of wavy-walled, flattened, chlorophylloid cells 
with thin cuticle and many stomata (breathing pores). Each stoma 
is surrounded by a pair of crescent-shaped guard cells which regulate 
its opening and closing. The upper and lower epidermis are con- 
tinuous around the laminar margin. 
Comparative Physiology of Root, Stem and Leaf (Frond). — The 
primary function of the roots of the Male Fern is that of absorption 
of water with mineral salts in solution. The secondary function 
is that of support for the stem, the tertiary, that of storing food- 
stuffs to tide the plant over the season when vegetative activities 
are lessened. Water is the most essential of all materials absorbed 
by vegetable organisms. It is found in the soil surrounding the 
soil particles with certain mineral salts dissolved in it. The delicate 
root-hairs with thin cellulose walls, protoplasmic lining and sap 
denser than the soil water, are firmly adherent to these particles. 
The soil water diffuses through these walls by osmosis and comes into 
relation with the ectoplasm, a delicate protoplasmic membrane which 
has the power of selecting what it wants and rejecting what it does 
not need. In this way only such solutes as are of value to the plant 
are admitted. The water with mineral salts in solution, once within 
the root-hair protoplast, is called “crude sap.” This passes through 
the hair into the cortical parenchyma cells which are in contact with 
the spiral ducts and scalariform tracheids. It passes from one cortex 
cell to another by osmosis and, under considerable root pressure, is 
forced into the spiral and scalariform tubes of the xylem. Therein 
it is conveyed upward by root pressure through the tracheids of the 
stem bundles into those of the leaves and finally osmoses into the 
leaf parenchyme cells (mesophyll). 
Carbon dioxide, (C0 2 ), from the air enters the leaf through the 
stomata. From the stomata it moves through the intercellular air 
spaces to the mesophyll cells which line these, whence it is absorbed. 
Within the mesophyll cells are found small chloroplasts composed 
of protoplasm and chlorophyll. The kinetic energy of the sun’s rays 
is absorbed by the chlorophyll which is thus energized to break up 
the C0 2 and H 2 0 into their component elements C, H and O, and 
rearrange them in such a way as to ultimately form sugar or starch. 
This process is called photosynthesis. According to von Baeyer, 
