14 Mr. H. J. Carter on the Development of the Root-cell 



necessary to extend these researcbes^ that I might ascertain also 

 the changes which the nucleus presents in the freshwater Algre 

 under cell-division, and having again chosen the roots of Cliara 

 verticillata for this purpose, I have been led to observe other 

 features in the protoplasm which I had not before noticed, but 

 which, together with the changes exhibited by the nucleus, I will 

 now also describe. 



Previously, however, it is advisable that I should state shortly, 

 what has been published respecting the development of the roots 

 of Chara, as well as that which is known of the formation of the 

 nucleus generally, in the Vegetable Kingdom. 



As regards theformei', it has already been stated by C. Miiller, 

 in his excellent description of the development of Chara"^, that 

 " as soon as the nucleary membrane [embryo-sac] began to burst 

 through the sporular membrane [brown- coat], like a bladder, 

 and to expand it in a sacciform manner [to form the first cell of 

 the plant-stem], it began to be developed in a sacciform manner 

 on the opposite side " [to form the roots] . Nothing afterwards 

 is mentioned about the roots, saving that " each utricle forms a 

 rootlet, and others follow it from simple vesicular expansion of 

 the nuclear membrane, so that it acquires at this end a complete 

 head of root-fibrilsf.^' 



For what is known respecting the formation of the nucleus in 

 the Vegetable Kingdom, I can quote nothing better than the 

 result of Nageli^s researches, which he has summed up in the 

 following manner, viz. : — "The nucleus originates in two ways; 

 either free in the contents of the cell, or by division of a parent 

 nucleus J." The first mode is witnessed in the embryo-sac of the 

 Phanerogamia [Scilla cernua, &c.), wherein "globular drops of 

 perfectly homogeneous mucilage with a defined outline" appear; 

 after which the larger ones present an " enclosed ring ;" and of 

 these, he adds, " there can be no doubt, for the further deve- 

 lopment also confirms it, that the mucilage-globule is a cell- 

 nucleus, the enclosed ring a nucleolus." He is also of " opinion 

 that the nucleolus originates first, and the nucleus subsequently 

 around it§;" lastly, he observes, "certain phsenomena connect 

 themselves readily with the hypothesis that they [the nucleoli] 

 are utricles ||." 



As regards the second mode of origin, viz. that by division, 

 this is witnessed in the nuclei which are formed on each side of 



* Ann. and Mag. Nat. Hist. vol. xvii. p. 254, 1846. 

 t Idem, p. 259. 



X Henfrey's Translations, Ray Soc. Pub. " Reports and Papers on 

 Botany," 1849, p. 168. 



§ Idem, pp. 106 & 107. 11 Idem, p. 172. 



