SIMPLEST FORMS OF GENERATIVE PROCESS. 



437 



forth, however, where the sporangium is developed within one of them. 

 The second form of the true generative process is seen even in the 

 higher Algae ; and, although the extent of its prevalence has not yet 

 been clearly determined, it is probably common to the Liverworts, 

 Mosses, and Ferns, it being in the last of these groups that it has been 

 most satisfactorily made out. In conformity with the separation or 

 specialization of organs which is characteristic of these Plants, we find 

 that the Generative power is now limited to certain small parts of them, 

 and that these produce two orders of cells, very distinct in their endow- 

 ments, which may be called respectively " sperm-cells," and "germ- 

 cells." It is from the latter that the new plant originates ; but this it 

 can only do, when the fertilizing influence of the former has been con- 

 veyed to it ; and the provision for this purpose is very remarkable. 

 The sperm-cells, developed within bodies termed antheridia, form in 

 their interior, as their characteristic products, minute spirally-coiled 

 filaments, usually furnished with cilia at one extremity, and bearing a 

 very close resemblance to the spermatozoa of animals ( 785). These, 

 when liberated from the cells within which they were formed, possess a 

 very active power of movement, in virtue of which they lake their way 

 to the germ-cells ; and when they have impinged against these, there is 

 reason to believe that they dissolve away, and that the product of their 

 diffluence is absorbed into the germ-cells and mingles with the contents 

 of the latter, the formation of a germ being the result of this intermix- 

 ture (Fig. 134, B). Here, then, we have the distinction of sexes well 



Diagram representing the three principal forms of the Generative process in Plants: A, conjugation of 

 inferior Cryptogamia; formation of the sporangium, b, by admixture of the discharged endochromes of the 

 parent-cells, a, a; 2, production of the sporangium, 6, within a dilatation formed by the union of the two 

 parent-cells; 3, production of the sporangium, b, by the passage of the endochrome of cell a into that of cell 

 a*, marking out a sexual difference. B. fertilization of germ in higher Cryptogamia; a, sperm-cell discharg- 

 ing its spiral filament, a*, germ-cell, against which one of these filaments is impinging, b, germ produced 

 by their contact. c, fertilization of germ in Phauerogamia; a, germ-cell, or pollen-grain, sending its pro- 

 longed tube down the style, until it reaches a*, the germ-cell, inclosed in the ovule, the section of whose 

 coats is shown at c; from the contact of the two, is produced the germ, 6. 



marked ; but both sperm-cells and germ-cells are usually developed in 

 the same organism, and are alike the product of a single original germ. 

 Throughout the Cryptogamic series, the fertilized germ appears to be 



