LIFE HISTORY OF THE MALE FERN 
19 
C0 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 (C 6 Hi 2 0 6 ). 
The formation of starch may be expressed by the following equation: 
6C0 2 + 5H 2 0 = C 6 H 10 O 5 + 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. 2 ) (pi. sori) and contains many sporangia. Each sporan- 
gium is composed of: (a) the stalk of considerable length and usually 
comprising three rows of cells, outgrowths of the epidermis of the 
pinmile; and ( b ) the head, sub-globular and hollow, consisting for 
the most part of a covering of thin walled, flattened cells within 
which will be noted a marginal ring of cells with walls having 
U-shaped thickenings and called the annulus. 
Within the sporangium are found the spores. Each spore is a 
single cell composed of an outer brown wall with band-like markings 
called an exosporium, an inner thinner wall or endosporium, and within 
this a mass of protoplasm containing a nucleus. 
