cing in the youngest parts of plants by the appearance of granules of 

 various sizes in a kind of mucilage, which contains the nutritive ma- 

 terials, some of which collect together into one body, which encloses 

 within it a rounded spherule : this mass so constituted he terms a cy- 

 toblast.* As soon as this has attained its full size, on some part of 

 its circumference can be observed a pellucid glassy border, which in- 

 creases in size and contains a gelatinous fluid; this border is the 

 commencement of a minute vesicle, which continues to enlarge, and 

 ultimately attains the perfect character of a cell ; and the cytoblast, 

 having performed its duty, becomes less and less, and in the majority 

 of cases is entirely absorbed, t 



Having examined nascent tissues since Schleiden's memoir on 

 Phijtogenesis, I am able to state that I have observed satisfactorily 

 most of the appearances he describes that are connected with this 

 subject; but still, I am under the necessity of stating that there are 

 two other methods that others and myself also have often witnessed, 

 by which cells are formed without the aid of a cytoblast, and the pro- 

 cesses are quite as perfect. These methods are very well seen in some 

 Conferva and in some species of Nosloc, where a diaphragm is deve- 

 loped across the interior of a cell and divides it into two perfect ones, 

 and this act is continually repeated. In Chara, as observed by Ami J 

 ci, and in Torula cerevisice, it is to be noticed that the young cell first 

 appears as a small bud projecting from the margin of a perfect cell ; 

 this eventually enlarges, becomes hollow, and takes upon itself the 

 same action : and in Ergoialia. abortifaciens I have described % the 

 fact that both kinds of formations of cells may be witnessed in that 

 very minute plant. 



Respecting the origin of the membranous tube of a vessel, many 

 theories have been advanced. Raspail says § that a vessel is created 

 from a globule on the external wall of another vessel, and that a cell 

 is created from a globule on the internal surface of another cell. And 

 from this difference the vessel can elongate by insinuating itself be- 

 tween the tissues, and the cell, being confined in the interior of ano- 

 ther, cannot assume an elongated form, and therefore he accounts for 



* This body had beca before described by Mr. Brown under the name of nucleus. 

 f It is a singular fact, discovered by Schwann, that animal cellular tissue is pro- 

 duced by an analogous method. 



X Linn. Trans, xviii. pt 3. 

 § Nouveau Systeme de Physiologie Vegetale, § 620. 



