40 
PHARMACEUTICAL BOTANY 
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 C 0 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, 
C 0 2 is split into C and 0 2 , the C being retained, the 0 2 given off. 
The nascent C is linked with H 2 0 to form CH 2 0 (formic-aldehyde); 
six molecules of this are then united to form grape sugar (C6 Hi 2 0 6 ). 
The formation of starch may be expressed by the following equation: 
6 C 0 2 + 5H 2 0 = C 6 Hio 0 6 + 60 2 . A portion of the grape sugar is 
removed from solution by the chloroplast and converted into starch 
which is stored up within it; another portion is used to nourish the 
protoplasm of the cell. But the greater portion of sugar manu¬ 
factured descends in solution through the phloem cells of the bundles 
of the veins, mid-rib and stipe to the stem or roots, where it is re¬ 
moved from solution by the action of the leucoplasts which convert 
it into reserve starch. Sugar and starch, however, are not the only 
food materials manufactured in the leaf. Proteins are likewise 
formed. These are composed of carbon, hydrogen, oxygen, nitrogen, 
sulphur and sometimes phosphorus. They are formed from grape 
sugar with the addition of nitrogen and the other elements by the 
living protoplasm. The source of nitrogen, sulphur and phos¬ 
phorus is the mineral salts which are found in the crude sap. These 
proteins descend through the sieve tubes of the veins, midrib and 
petiole to the stem and roots, nourishing all of these parts with protein 
material. 
Gross Structure and Histology of the Sori and Sporangia. —The 
sporangia or spore cases are found clustered together in circular 
groups on the under surface of the pinnules nearer the mid-vein than 
the margin. Each group of sporangia is covered with a membranous 
expansion of the epidermis called the indusium. The whole is called 
a sorus (Fig. 12) (pi. sori) and contains many sporangia. Each 
sporangium is composed of: (a) the stalk of considerable length and 
usually comprising three rows of cells, outgrowths of the epidermis of 
the. pinnule ; and ( b ) the head, sub-globular and hollow, consisting for 
the most part of a covering of thin walled, flattened cells, within 
