FERTILIZATION AND FRUIT-FORMATION IN CB yPl'OGAMS. 49 



ontinue to use them with advantage. Thus, under the name of Cryptogam we 

 hall include all plants destitute of flowers in the ordinary sense and possessing 

 rgans of fructification which are not clearly visible excepting under the microscope 

 rhilst the term Phanerogam will comprise such plants as bear flowers, and have 

 rgans of fructification which are visible without aid from the microscope and are of 

 he nature of metamorphosed leaves. The retention of these old and familiar terms 

 3 rendered all the more desirable by the fact that another important distinction, 

 Fhich is inherent in the process of fertilization itself, and has not as yet received 

 uiBcient attention, is involved in the separation of Cryptogams and Phanerogams, 

 lamely, that in Cryptogams fertilization takes place in water or in a watery 

 Qedium, whereas the process in Phanerogams is accomplished almost exclusively in 

 he air. 



FERTILIZATION AND FRUIT-FORMATION IN CRYPTOGAMS. 



In the mountain districts of Central Europe, after the winter snow has melted 

 md the turbid water derived from it has gradually cleared itself up, a beautiful 

 light is afforded, especially when a ray of sunshine strikes the water, by the dense 

 ;rowds of short delicate filaments of a bright emerald-green colour, which every- 

 where form a coating to the stones at the bottom of streams and to the sides of the 

 iroughs used to convey spring-water from the heights. These green threads belong 

 ;o a plant named TJlothrix. Each separate filament consists of numerous cells joined 

 iogether so as to form a chain, as is shown in fig. 201 ^. When these filaments are 

 nature, and the time has come for the production of fruit, the protoplasmic contents 

 )f the separate cells break up into a number of spherical green masses, which, how- 

 )ver, continue to be held together in a rounded cluster by means of a colourless 

 lubstance. An aperture is now formed in the wall of each of the cells in question, 

 md through this opening the conglomerate mass escapes into the surrounding water 

 see figs. 201 ^ and 201^). The individual masses of protoplasm which compose the con- 

 glomerate are set free shortly afterwards, and each exhibits at its anterior extremity 

 I. pair of revolving cilia, by means of which it swims about in the water (fig. 201 *). 

 When in the course of their peregrinations two protoplasts which originated in 

 me and the same cell-cavity encounter one another they get out of each other's way; 

 f, on the other hand, the protoplasts from cells belonging to different filaments 

 neet, far from avoiding one another, they come into full collision with their anterior 

 liliated extremities, turn over, and lay themselves side by side and coalesce, forming 

 \, single body with four cilia (see fig. 201 °). A little later the cilia vanish, and 

 he product of the coalescence comes to rest. This fusion is the gimplest conceivable 

 ;ase of fertilization in the whole realm of plants. The product of fertilization is 

 he fruit. It consists in Ulothrix of the little lump of protoplasm formed by the 

 )rocess of coalescence just described, which now surrounds itself with a thick cell- 

 nembrane, and fastens on to some stationary body under water (see fig. 201 ®). We 

 lave nothing to do at present with the subsequent development of this fruit ; it is 



VOL. II. 84 



