LIFE HISTORY OF A FERN. 235 



of cells are found in close contact and intimately united, and they 

 there form cellular tissue. But in the life-history of every plant 

 there is one period when certain of these cells become isolated 

 and commence an independent existence as pollen-grains, spores, 

 gem mules, etc. 



We may commence our review of the life-history of a Fern at 

 this period of independent cell-existence — that is, with a spore, in 

 which condition each separate individual is complete in itself, and 

 possesses all the potentialities of the perfected plant. 



Taking a mature leaf of Fern, we shall find upon the under- 

 side a number of bodies differing in form and arrangement in 

 different species. These are the cases, or sori, in which the spores 

 are formed, and by which they are covered until they are fully 

 developed. In the Polypody they are distinct, round, yellow 

 spots ; in the Male Fern, they are brown, smaller, and more 

 numerous ; in the Hart's tongue they assume the form of elon- 

 gated rows ; while in the Bracken the edges of the leaf are rolled 

 back to form the covering. If a leaf bearing these sori is laid 

 back downwards on a piece of paper, in a few days a quantity of 

 exceedingly fine powder will be found to have escaped from the 

 spore-cases. This is the fabled "" Fern seed," whose mysterious 

 power of rendering its possessor invisible has formed the subject 

 of many an old-world legend. This powder, however, does not 

 consist of seeds, but spores, and there is a wide distinction 

 between the two which we may for a moment profitably consider. 



Seeds are defined as " independent reproductive bodies, con- 

 taining an embryo or rudimentary plant at the time when they are 

 cast off by the parent." Take any ordinary seed (a pea or bean 

 may be selected because of their size and familiarity), and carefully 

 divide it through the centre so as to disclose the interior, and it 

 will be found to consist of three parts : — first, the outer skin or 

 shell ; within this a quantity of albuminous matter (which, how- 

 ever, is not present in all seeds) ; and embedded in this fleshy 

 substance a small body, usually curled more or less into a semi- 

 circular form, which is the embryo or rudimentary plant. When 

 germination commences, the embryo throws out a tiny rootlet, 

 which grows downwards, and an upright stem with leaves pushes 

 itself upwards through the soil. Here in the embryo we have all 



