of Hippuris vulgaris. 263 



series of researches, as far as they go, among the many to which 

 this controversy has given origin. ' The facts which are brought 

 forward by this author are confirmatory in the most important 

 particulars of what had previously been ascertained by Hof- 

 meister, linger, and others, but are distinguished by the author's 

 inquiries having been carried to an earlier period in the develop- 

 ment than had been arrived at by any previous observer in the 

 families to which they refer, namely the Scrophulariacea and the 

 Crucifera. 



In the Scrophulariacea generally, as in Hippuris, the embryo- 

 vesicle assumes at an early period an elongated form, and its 

 subsequent development is identical. Tulasne has traced it to 

 its earliest origin in several species. He has shown that it is 

 developed originally on the inner surface of the wall of the em- 

 bryonal sac near its summit, but at a point quite separate from 

 that at which the pollen-tube is applied. This vesicle, at first 

 exceedingly minute, grows upwards in the cavity of the embryo- 

 sac, until it assumes a form similar to that seen in Hippuris. 

 These facts are important, as serving to point out more distinctly 

 the strict correspondence between the morphological modifications 

 of the same development as observed in the Scrophulariacea and 

 other orders, with those possessed of distinct embryo-sacs, as the 

 Orchidacecs. 



The researches before us also derive an additional interest 

 from their showing the total inaccuracy of the observations of 

 . Prof. Wydler of Berne, (which were made on the same natural 

 order,) who in the year 1838 set himself to support the theory 

 of Schleiden, and from whose alleged facts that physiologist de- 

 rived some of the most powerful supports of his views. 



In the Crucifera M. Tulasne has also accomplished all that 

 can be done to perfect our knowledge of the embryogeny of the 

 order. In particular he has described and figured distinctly the 

 embryonal sac, the existence of which was doubted in that order, 

 and has traced the embryonal vesicle from its earliest condition, 

 that of a minute cellule attached to the micropyle extremity 

 of the embryo-sac, up to that of a cylindriform cell filled with a 

 granular protoplasm, at the period at which it should seem that 

 fertilization takes place. 



Numerous other points of great importance might be men- 

 tioned as illustrated by this admirable series of researches. They 

 will well reward the perusal of all who take any interest in vege- 

 table anatomy and physiology, and they are illustrated by draw- 

 ings, which exceed in beauty and detail all their predecessors, 

 although many of these have been beyond all praise. 



From the accurate knowledge of the facts connected with the 

 origin and development of the vegetable embryo, into the pos- 



