68 PHARMACEUTICAL BOTANY 
sporophyte number, so that each spore contains only half the 
number of chromosomes found in the sporophyte generation and 
thus belongs to the gametophyte generation. 
Each spore is a single cell composed of an outer brown wall 
with band-like markings called an exosporium, an inner thinner 
wall or endosportum, and within this a mass of protoplasm con- 
taining a nucleus. 
The sporophyte generation ends with division of the spore 
mother cell to form a tetrad of young spores. 
HisToRY OF THE GAMETOPHTYE OR SEXUAL GENERATION 
The gametophyte generation begins with the tetrad of young 
spores within the sporangium. 
RupTurE OF SPORANGIUM AND SporE DissEMINATION.—As was 
previously indicated, each sporangial head had a row of cells 
with U-shaped thickenings around the margin called an annulus. 
As the sporangium matures, the water escapes from the cells, 
pulling them together and holding the annulus like a bent spring. 
The thinner walled cells at the side of the spore case opposite 
the annulus, unable to stand the strain, are consequently torn; 
the annulus then straightens and a wide rent is made in the 
sporangium. The annulus then recoils and hurls the spores out 
of the sporangium. 
GERMINATION.—The fern spore, falling upon a moist surface, 
germinates, producing a delicate, green, septate filament called a 
protonema. One end of this structure shows larger cells, which, 
by the formation of oblique walls, cut out an apical cell of some- 
what triangular shape. This is the growing point of what 
eventually becomes a mature, green, heart-shaped body called 
the “‘prothallium” or “prothallus”? The prothallium, about the 
size of an infant’s finger nail, develops on its under surface 
antheridia, or male sexual organs, archegonia, or female sexual 
organs, and rhizoids or hair-like absorptive structures. The 
antheridia appear three to five weeks 
rid oo PRES in shape and are situated among the 
rhizoids toward the terior ‘5 ‘di : 
ppaniingastheiore + 5 = sei Each antheridium consists of 
pletely surrounds the 5 ermatocytes 
or mother-cells of the spermatozoids. Within each ose 
after spore germination. 
