.352 THE MICROSCOPE AND ITS REVELATIONS. 



CHAPTER IX. 

 OF THE MICROSCOPIC STRUCTURE OF PHANEROGAMIC PLANTS. 



349. BETWEEN the two great divisions of the Vegetable kingdom 

 which are known as Cryptogamia and Phanerogantia, the separation is 

 by no means so abrupt as it formerly seemed to be. For, as has been 

 already shown, though the Cryptogamia were formerly regarded as alto- 

 gether non-sexual, a true Generative process, requiring the concurrence 

 of male and female elements, is traceable throughout the series. And in 

 the higher type of that series, we have seen a foreshadowing of those 

 provisions for the nurture of the fertilized embryo, which constitute the 

 distinctive characters of the Phanerogamia. On the other hand, although 

 we are accustomed to speak of Phanerogamia as ' flowering-plants/ yet 

 iiot only are the conspicuous parts of the flower often wanting, but in the 

 important group of Gymnosperms (including the ConifercB and Cycadece), 

 the essential parts of the Generative apparatus are reduced to a condition 

 of extreme simplicity, closely approximating to that of the higher Cryp- 

 togams. There are, however, certain fundamental differences between 

 the modes in which the act of fertilization is performed in the two 

 groups. For (1) whilst in all the higher Cryptogams, it is in the condi- 

 tion of free-moving ' antherozoids ' that the contents of the sperm-cell 

 find their wa'y to the germ-cell, these are conveyed to it, throughout the 

 Phanerogamic series, by an extension of the lining membrane of the 

 , sperm-cell or pollen-grain into a tube, which penetrates to the germ-cell 

 contained in the interior of the body called the 'ovule.' Again (2), 

 while the 'germ-cell ' or ob'sphere in the higher Cryptogams is contained 

 in a structure that originated in a spore detached from the parent- plant, 

 it is not only formed and fertilized in all Phanerogams whilst still borne 

 on the parent fabric, but continues for some time to draw from it the 

 nutriment it requires for its development into the 'embryo.' And at the 

 time of its detachment from the parent, the matured * seed ' contains, 

 not merely an ' embryo ' already advanced a considerable stage, but a 

 .store of nutriment to serve for its further development during germina- 

 tion. As there is nothing parallel to this among Cryptogams, it may be 

 said that reproduction by seeds, not the possession of flowers, is the dis- 

 tinctive character of Phanerogams. The ovules, which when fertilized 

 and matured become seeds, are developed from specially modified leaves, 

 which remain open in Gymncteperms, but which, in all other Phanero- 

 gams, fold together so as to inclose the ovules within an 'ovary.' Each 

 ovule consists of a ' nucleus ' surrounded by ' integuments ' which remain 

 unclosed at its anterior end, leaving open a short canal termed the ' mi- 

 cropyle.' One cell of the nucleus undergoes great enlargement, and be- 

 comes the embryo-sac, whose cavity is filled, in the first instance, with a 



