248 THE PHENOMENON OF 



of the cells of the embryo of the Phanerogamia, and in 

 many cases even the formation of the endosperm-cells.* 

 Numerous researches on this kind of cell-formation agree 

 essentially in the following points : the nucleus of the 

 mother- cell is more or less completely dissolved ; in its 

 place are produced two new nuclei, either near together, 

 or at a distance. Between these suddenly appears a line 

 of division (really a plane of division) which indicates a 

 parting of the cell-contents into two portions, each of 

 which encloses one of the nuclei. The two portions of 

 contents are originally bounded only by their primordial 

 utricles, which immediately secrete a new cell-membrane 

 over the whole of their surface, and thus form a septum 

 between them at the surface of contact. Many observa- 

 tions testify that the two daughter-cells are completely 

 separated, by the shutting off of their primordial utricles, 

 before the origin of the septum. Thus Molilf frequently 

 observed two primordial utricles in one cell, in cambium, 

 as well as in the tips of stems and young leaves of various 

 plants ; Hofmeister^ represents such a case in the embryo 

 of Leucojum eestivum, and also, in the description of the 

 formation of the special mother-cells of the pollen of 

 Passiflora, and Pinus,*$ endeavours to show the formation 

 of the septum to be subsequent to the division of the pri- 

 mordial utricle. With regard to the behaviour of the nucleus, 

 it must be remarked, that according to the observations of 

 Mohl and Nageli, the formation of the two new nuclei takes 

 place in many cases through division of the nucleus of 

 the mother-cell || (without solution of this). It seems to 



* Hofmeister, ' Die Enstehung des Embryo der Phanerogamen,' 1849, ' 

 e. g., p. 35, t. xii. (Monotropa) ; p. 40, t. iii. (Bartonia.) 



t 'Bot. Zeitung.,' 1844, p. 290, (Trans, in 'Sc. Memoirs,' vol. iv, 

 p. 96. A. H.) 



J ' Die Enstehung des Embryo,' t. vi, f. 20. 



' Ueber Pollen,' ' Bot. Zeitung.,' 1848, pp. 654, 671. 



|| Vide Nageli, ' Zeitschrift,' 1844, p. 75. (Trans, in Ray Society's 

 publications, 1845, p. 254,) where is described, of Sphacelaria, a division of 

 the central nucleus of the mother-cell preceding the division of the cell, 

 while in Zonaria Pavonia, and Cystoseira, the parent nucleus is said to 



