12-i ANATOMY AND PHYSIOLOaY OF 



Eqnisetacese of an irregular mass of cells divided into many lobes. 

 The development of tlie pro-embryo is extremely simple in these 

 plants. The spore-coat (fig. 50 c. d.) becomes expanded in germi- 

 nation, bursts througli the outer membrane of the spore, sends out 

 hair-like prolongations serving as rootlets on one side, and becomes 

 prolonged on the other into the form of a cylindrical cell, which 

 becoming divided by septa into a number of cells, and so on by 

 continued growth and cell-multiplication, is gradually developed 

 into the perfect pro-embryo. In these plants no part of the spore 

 seems to be pre-determined for the production of the said parts, but 

 every point of it to be cajDable of the development described ac- 

 cording to the position in which it may be placed. 



But the germination of the large spores of Lycopodium, Mar- 

 silsa, Pilularia, Salvinia, and Isoetes, is more complicated ; in 

 them not only is that part of the spore, which by the contiguity 

 of the four cells in each parent-cell, has acquired a more or less 

 evidently three-sided pyramidal form, the only germinal point of 

 it, but the pro-embryo is developed up to a certain stage in the 

 interior of the spores, and issues from the rent in the outer spore- 

 coat, as an already parenchymatous structure, of diflEerent form in 

 different genera. 



The pro-embryo of the Mosses is capable of transforming one or 

 more of the cells seated upon its various ramifications, immedi- 

 ately into buds, which grow up into leafy stems, so that here we 

 have the peculiar condition of one spore giving rise to the deve- 

 lopment of a number of plants. 



The pro-embr3^os of Ferns, Ehizosperme^, Equisetacese, and Lyco- 

 podiacese, on the contrary, are incapable of the immediate produc- 

 tion of leaf-buds, and produce upon the uppermost layer of cells, 

 one, or mostly a number of peculiarly-formed organs, which, fol- 

 lowing the example of Leszcyc-Suminsld, are called ovules, from 

 whicli organs, but not until after an impregnation by the anther- 

 idia, which discharge their contents at the same time, the future 

 plant gi'ows out under the form of a bud ; when this impregnation 

 fails, tlae pro-embryo remains infertile. 



In the Ferns and Equisetaeese the pro-embryo produces the an- 

 theridia with the ovules, at the same epoch ; in the Bhizocarpese, 

 on the contrary, the parent plant which furnishes the large spores, 

 forms at the same time smaller, for the purpose of producing an- 

 theridia, and these small spores, as already mentioned, in like man- 

 ner exhibit a kind of germination, the product of which consists 

 not of an embryo, but of antheridial cells. In the Lycopodiacese 

 the conditions are still obscure, (8ee note p. 121.) 



The ovule consists of a large cell belonging to the tissue of the 

 pro-embryo, with four cells or rows of cells overlapping it on the 

 outer surface of the pro-embryo, and leaving an intercellular pas- 

 sage between them leading down from the open air to that cell. 

 ' Count Leszcyc-Suminski, the discoverer of these ovules in the 



