684 MICROSCOPIC STRUCTURE OF PHANEROGAMIC PLANTS 



CHAPTER XI 



OF THE MICROSCOPIC STRUCTURE OF PHANEROGAMIC PLANTS 



BETWEEN the two great divisions of the Vegetable Kingdom which 

 are known as Cryptogamia and Phanerogamia 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 

 altogether non-sexual, a true generative process, requiring the 

 concurrence of male and female elements, is traceable almost through- 

 out the series. And in the higher types of that series we have seen 

 a foreshadowing of those provisions for the nurture of the fertilised 

 embryo which constitute the distinctive characters of the Phanero- 

 gamia. On the other hand, although we are accustomed to speak of 

 Phanerogamia as ' flowering plants,' yet not only are the conspicuous 

 parts of the flower often wanting, but in the important group of 

 Gymnosperms (including the Conifercv and Cycadece) the essential 

 parts of the generative apparatus are reduced to a condition closely 

 approximating to that of the higher Cryptogams. There are, how- 

 ever, certain fundamental differences between the modes in which 

 the act of fertilisation is performed in the two groups. For (1) 

 whilst in all the higher Cryptogams it is in the condition of free- 

 moving * antherozoids ' that the contents of the sperm-cell find their 

 w T ay 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. 1 Again 

 (2), while the ' germ-cell ' or oosphere 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 fertilised 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 



1 A very remarkable and interesting discovery, for which we are largely indebted 

 to the brilliant observations of two Japanese botanists, Professors Ikeno and Hirase, 

 has recently thrown great light on the approximation referred to by Dr. Carpenter 

 between the higher Cryptogamia and the lower Phanerogamia. It is now known 

 that in both the larger groups of Gymnosperms, the Coniferae and the Cycadeas, there 

 are species in which the fertilising body is a motile antherozoid formed within a 

 pollen-tube, thus combining the distinctive modes of fertilisation characteristic of 

 the two great sections of the vegetable kingdom. As Dr. Carpenter does not include in 

 his account of the ' Microscopic Structure of Phanerogamic Plants ' a full description 

 of the mode of impregnation in flowering plants, the reader is referred, for further 

 details, to the most recent Text-books of Botany, or to the Summary of Current Re- 

 searches in Botany in the Journal of the R. Microscopical Society. EDITOB.] 



