anthers and carpels. In the Bracken they arise on the ordinary 

 foliage-leaves. We have now to trace out the life-history of the 

 plant from such spores. To find them we must examine the under- 

 surface of a leaf, and if spore-cases are present, we shall discover 

 them within a narrow fold of the margin. The groups of spore- 

 cases are called sori {sonts, a heap). Each separate case 

 (sporangium) is at the end of a stalk, and contains, when ripe, a 

 number of spores, which are much like invisible pollen-grains. An 

 elastic-ring round the spore-case, by its contraction, causes the case 

 to burst, thus allowing the spores to escape. When a spore, in 

 which the future energy of the fern is stored, falls on suitable soil, 

 a row of green cells creeps out, and these cells ultimately develop 

 into a small green film some eighth of an inch across. This is 

 heart-shaped with a notch at the broader end, and is calkd the 

 prothallium. It is very thin except near the notch. On the under 

 surface of the thicker cushion, little tubes are formed, at the base 

 of each of which is an egg-like spore. Farther back amongst a 

 number of hairs are some other short tubes, antheridia, which 

 produce what are called antherozoids, minute atoms of living 

 matter — quite invisible — with several threads of protoplasm pro- 

 truding from them. By the aid of these threads the antherozoids 

 are able to swim about in the film of moisture beneath the pro- 

 thallium till they find an egg and fertilize it. 



From a simple cell — the spore — in which all its future was as it 

 were stored, the fern started. It has passed through the prothallium- 

 stage, and now again has its very essence stored up in a single cell 

 — the egg-spore. Thus it has completed one generation of its life- 

 cycle. The egg-spore develops, not into a prothallium, but into a 

 tiny fern-plant, this appearing at the notch. Now the prothallium 

 dies. The plant grows up, and ultimately produces spores of the 

 first kind on its leaves, thus completing the second generation. 

 This is the life-cycle of a fern and its allies. We started with a 

 spore and we have arrived at a spore of the same kind again. 



It will be noticed that by a generation we mean that part of the 

 life-cycle of an organism, which extends between the points, when 

 its whole energy and essence is shut up in a single cell. Twice in 

 the life of the Bracken (and all ferns) this occurs. Its life, there- 

 fore, consists of two generations. Further, the form and activity 

 of the plant during the two stages between the single-cell states are 

 very diii'erent. When this is the case we say that the organism 

 passes through an " alternation of generations." The flowering- 

 plants do so in a way, but to most persons the process is a hidden 

 one. The moss plant has two distinct generations also and the 

 same two kinds of spores, but the conditions between are so 

 different from those of the fern that it does not seem possible for 

 the fern tribes to be the offspring of the moss- tribes. Maybe they 

 followed two lines of descent from common ancestors amongst the 

 algal division of the cellular cryptograms. 



