of Hippuris vulgaris. 265 



served after animal impregnation is the development of two 

 cells in the germ-vesicle. These cells then multiply to a greater 

 or less extent by transverse division so as to form a confervoid 

 filament. At last, either at the centre or termination of this fila- 

 ment, one cell becomes developed by an endogenous mode of cell- 

 production into a body to which the term embryo-globule is 

 applied, and which is in fact the future embryo, while the rest 

 perform a subordinate function, being probably merely subser- 

 vient to the nutrition of the embryo. This last process corre- 

 sponds in animals to the successive divisions of the two cells 

 previously referred to, what is called the " cleaving of the yelk 

 mass/^ on the surface of which the embryo is subsequently de- 

 veloped. 



The foregoing sketch of what may be considered as the morpho- 

 logical type of the embryogenic development in the higher plants 

 will, it is believed, include all those modifications which occur in 

 those families which have been hitherto investigated. And consi- 

 dering that of late years, since the means of research have been so 

 much more complete than formerly, there has been such a remark- 

 able consonance in the results obtained by diff'erent observers, 

 there is little reason to apprehend that any new facts are likely to 

 arise, which will render it necessary to modify our generalizations 

 to any great degree. We may therefore consider the controversy 

 for the present settled. The doctrine of Schleiden is now only 

 a matter of history, and as such possesses very great interest. 

 When in 1837 he first brought forward his splendid discoveries 

 as to the previously unknown nature and functions of cells, he 

 founded upon them another doctrine, according to which the 

 existence of sexes in plants was denied, and the so-called male 

 organ alone was supposed to originate the germ. The history 

 of this celebrated doctrine exemplifies in a remarkable manner 

 the truth of the observation, that, although false facts may do 

 an infinity of mischief in science, false theories are often produc- 

 tive of the greatest benefit. 



The numerous researches which have been set on foot within 

 the last ten years with a view to the refutation of the doctrines 

 of Schleiden, have not only established the utter baselessness of 

 these last, but have furnished us with a series of details more 

 complete and more conclusive than any which we possess in con- 

 nection with any other subject in the whole range of vegetable 

 anatomy. 



