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the Osmundas, green, and contained in small stalked capsules 

 which occur in clusters of various shapes. In the Polypodies 

 these clusters, heaps or sori (sorus, a heap), are round and un- 

 covered, but in most species the heaps are protected by some sort 

 of covering or indusium. The spore capsules, when ripe, burst 

 open very suddenly and expel the contained spores to some dis- 

 tance ; a few fresh capsules scattered on the field of a microscope 

 can be seen exploding like so many bomb-shells, scattering their 

 bullets in all directions. If now we place a few of these spores 

 on a damp piece of clay and cover them with a glass, in about a 

 fortnight in warm weather we shall see them, under a lens of 

 course, protrude a small green projection, a cell containing 

 chlorophyl, the active principle of all green vegetation. This 

 cell proceeds to multiply itself, splitting up and forming others, 

 first in a straight row of four or five, from several of which the 

 first root hairs will proceed, anchoring it as it were to the clay 

 and absorbing any nourishment they can get at the same time. 

 Presently, however, they begin to spread sideways as well as for- 

 ward, and in a week or two the familiar heart-shaped scale will 

 be completed. Meanwhile, upon its under surface, first of all 

 among the numerous root-hairs, a number of tiny pimple-like 

 bodies will have appeared ; these are the antheridia or male 

 organs, and later, close to the indentation of the heart, a small 

 cluster of longer ones originate, which are the archegonia or 

 female organs. Both these classes of organs are usually im- 

 mersed in the dew-like moisture that collects upon the under side 

 of the prothallus under congenial conditions of growth, and 

 in due time the antheridia burst and throw out an immense num- 

 ber of extremely small tadpole like bodies, which swim actively 

 about and make their way to the archegonia. At the base of 

 each archegonium is an egg-cell; this is fertilized by contact 

 and at once proceeds to split up into other cells, to swell and in 

 time to send down a root proper into the soil and a primary frond 

 into the air, and the fern is fairly launched on its career. It will 

 have been observed that a cluster of seed-cells is formed on each 

 prothallus, but though twin plants are by no means rare, only 

 one of these cells usually produces a plant, the prothallus seem- 

 ing incapable of supporting a number through the initial stages. 

 It has, however, been shown that by cutting the prothallus through 

 the cluster and so to some extent isolating the cells, each piece 

 will produce a plant. In some species, too, the prothallus buds 



