32 ON THE PLANT-CELL. 



and especially striking in some monocotyledonous orders, as Orchidece, 

 CommelinecB) and Asphodelece, also in many dicotyledonous orders, as the 

 Cactece, BalanophorecB, &c., in the entire leaves of Mosses, especially in 

 Sphagnum, we find in every cell, fastened to the inner wall, a small, 

 mostly plano-convex or lenticular, sharply defined body, strikingly dif- 

 ferent from all other contents of the cell. This is the cytoblast. It is 

 met with in all newly-formed cellular tissue, but later it disappears from 

 the same cells. It is seen in various stages of perfection. When per- 

 fectly formed, it is a fiat, lenticular, sharply defined, transparent, pale- 

 yellow body, in which it is easy to distinguish one or two, seldom three, 

 sharply defined and evidently hollow corpuscles, which are called nucleoli. 

 In its most imperfect form it appears merely as a flat, yellow, semi-granular 

 globule, in which there are no nucleoli, and which do not appear later. 

 It varies much in its character, according to the plant as well as its 

 age : in colour } from perfect clearness to a dark yellow grey ; by iodine it 

 is converted from a pale yellow to a dark brown : in consistence, from a 

 granular mucilage to a firm homogeneous mass : in the number of its 

 nucleoli, from one to three ; in the form of the same, from an entire 

 absence through a simple globule to one that is hollow : in its own 

 form, from the globular to the lenticular and to the egg-formed disc : in 

 its absolute size, from 0*00009 to 0-0022 of an inch in circumference : 

 in its relative size, from the cells which it fills to those in which it forms, 

 not more than the five-hundredth part of the inner surface of the cell- 

 wall ; and lastly, in its attachment to the cell-wall, from a loose adhesion 

 to a perfect union with the cell-wall and enclosure in a duplicature of the 

 same. With the exception of the nucleoli, the first statements relate 

 universally to the younger states of the cytoblast. 



In those cases in which I have been able to observe completely the 

 origin of the cytoblasts, as in the albumen (perisperm) of Chamddorea 

 Schiedeana, Phormium tenax, Colchicum autumnale, Pimelea drupacea, 

 and many papilionaceous plants, I have found that they appear at first 

 amongst the little mucus-granules of the formative fluid, and that they 

 are gradually accumulated around the nucleoli ; and as they combine 

 together to a greater or less degree, a thicker or thinner disc is formed, 

 and sometimes two or three such discs lie near one another, and at last 

 the cytoblast presents itself. All this takes place before a cell can be 

 seen.* In young cells I frequently found the cytoblast convex, granular, 

 yellow, with the nucleoli simple : in older cells of the same plant, flat, 

 homogeneous, uncoloured, the nucleoli hollow (e. g. Cactece). 



In the Cryptogamia the cytoblasts are not so generally seen, yet they 

 are present in the spores of Ferns, Mosses, Lichens, and some Fungi, and 

 now and then in the cellular tissue of Algae, and in the cells of Spiro- 

 gyra, free in the midst of the cell. 



A chemical analysis of the nucleoli is at present impracticable. 



That the cytoblast is a nitrogenous body, a protein-compound, and 

 perhaps in its simplest state pure protein, is proved by its colour, con- 

 sistence, behaviour towards liodine, alcohol, alkalies and acids, and 

 concentrated nitric acid ; and by the researches of Pay en, confirmed by 

 Mulder, on the protein-compounds in the spongioles and in the cambium, 

 compared with the microscopic analysis of those parts. 



Thus far extend my own observations, but recently Niigeli has con- 

 siderably enlarged them. (Schleiden and Niigeli, Zeitschrift fur Wis- 



* See Plate I. fig. 1. a, 1; 3.; 4. a, b ; 5., with the explanation. 



