PIIYTOGENESIS. 



many of the cells in the epidermis of the Orchidea, an opaque 

 spot, named by him areola, or nucleus of the cell. JIc subse- 

 quently pursued this phenomenon in the earlier stages of the 

 pollen-cells, in the young ovulum, in the tissue of the stigma, 

 not only in the Orclndcce, but also in many other Monocotyle- 

 dons, and even in some Dicotyledon*. 



As the constant presence of this areola in the cells of verv 

 young embryos and in the newly-formed albumen could not 

 fail to strike me in my extensive investigations into the deve- 

 lopment of the embryo, it was very natural that the consider- 

 ation of the various modes of its occurrence should lead to the 

 thought, that this nucleus of the cell must hold some close 

 relation to the development of the cell itself. I consequently 

 directed my attention particularly to this point, and was for- 

 tunate enough to see my endeavours crowned with success. 



Before, however, I proceed to the communication of these 

 observations, I must first give a somewhat more detailed 

 description of the nucleus. As I have to treat of a peculiar 

 and, I think, universal elementary organ of vegetables, I do 

 not consider it necessary to apologise for applying a definite 

 name to this body, and therefore call it Cytoblast (kvtoc, 

 fiXaaToq) in reference to its function, which will be described 

 hereafter. 



This formation varies in its outline from oval to circular, 

 according as the solid which it forms passes from the lenticular 

 into the perfectly spheroidal figure. I have found the oval 

 and flat cytoblasts more frequently in Monocotyledons, in the 

 albumen and pollen ; the globular chiefly in the Dicotyledons, 

 and in the leaf, stem, articulated hairs, and similar structures ; 

 no exclusive rule, how r ever, can be laid down on this point. 



The colour of the cytoblast is in general yellowish, but it 

 sometimes passes into an almost silvery white. I remarked it 

 as being most transparent in the albumen of sonic wat. I 

 plants, in the unripe pollen, in some Orc/tidcw, and also in the 

 rudiments of the leaf of Crassula portulaca. Its excessive 

 transparency renders it scarcely perceptible in the spores of 

 some Helvelloids. It is coloured by iodine, according to its 

 various modifications, from a pale yellow to the darkest brown. 



It varies considerably in size. It is in general largest in 

 Monocotyledons, and in the albumen; and smallest in DtCO- 



