REJUVENESCENCE IN NATURE. 249 



me very doubtful v^hetlier two different conditions of this 

 case really occur, since a rapid reconstruction of the 

 nuclei of the daughter-cells out of the still accumulated 

 mass of the nucleus of the mother-cell, in a state of 

 solution at its periphery, may readily be looked upon as 

 a division of the latter. 



How far either the partition of the primordial utricle, 

 or the formation of the dissepiment between them, is 

 really, or only apparently, simultaneous over the whole 

 face, can scarcely be decided in the present stage of 

 observation. Very few observations speak in favour of 

 the latter assumption. In one case, certainly referring 

 here, namely, to the " young-cell-division," in the forma- 

 tion of the stomate-cells (see the preceding note), Mohl 

 asserts that he observed the formation of a septum 

 beginning with the production of an annular ridge. I 

 should consider as an indication that the division of the 

 primordial utricle .also begins at the periphery, the 

 formation of the at jBrst simple zone of granules, subse- 

 quently doubled by a clear line of division, at the equator 

 of mother-cells of the pollen of Pinus* preparing for 

 division, and already provided with two nuclei, — a phe- 

 nomenon which seems to indicate a conflict of the two 

 newly-formed centres, expressing itself fii'st of all at the 

 periphery of the plane of division, when they are defining 

 their boundaries. I shall hereafter mention a structure 



vanish, and be replaced by two new ones. Nageli further describes the 

 division of the nucleus in title cells of the hairs of the stamens oi Tradescantia 

 (1. c, p. 67; Ibid., 1847, p. 102— Translation in Ray, vols., 1845, p. 246, 

 1849, p. 168,) while according to Hofmeister, ('Enst. des Embryo,' p. 8, 

 t. xiv, figs. 20, 28) the membrane of the parent nucleus is absorbed, so that 

 only the mucilaginous and no longer sharply defined body of its contents, is 

 divided into two globular balls, which become the new nuclei. According 

 to Mohl, ('Vermischte Schriften,' p. 252,) the nucleus of the mother-cell 

 becomes divided, in the formation of stomates, to form the nuclei for the 

 two boundary cells of the stomatal opening. According to Nageli, ('Linnaja, 

 1842, p. 237,) on the other hand, the formation of the two new nuclei is 

 preceded by a disappearance of the nucleus of the mother-oeU. 



* Hofmeister, 'Bot. Zeit.,' 1848, p. 671, t. vi, f. 22, 24. In Passiflora, 

 on the contrary, the zone of granules is replaced by a granular plate occupy- 

 ing the whole surface of division. See t. vi, f. 8, 9. 



