Sinidure and Division of the Vegetable Cell. 195 



Ornitliogalum 'pyramidale, various. 



Golchicum autumnale, leaf epidermis and parenchyma cells. 



Pathos, sp., leaf epidermis. 



Saccharuni officinarum, cells from young stem. 



Cryptogams. 



Equisetum limosum, cells from young stem. 

 Chara fragilis. 

 Splrogyra nitida. 



The cells of the stem and leaf-epidermis of Fritillaria 

 imimrialis show the largest examples of the new structure, 

 but it is very distinct in Ornithogalum pyramidale, and 

 Narcissus Pseudonarcissus. In the cylindrical cells of 

 Spirogyra there is a difficulty, at times, to demonstrate it 

 owing to their roundness, but in Plate X. fig. 1, it is very 

 evident. Usually there is only one, but it is by no means 

 uncommon to find two, and even three or four. When more 

 than two are present, however, the cells are generally old ; 

 and this is a significant fact. The new structure is round 

 or slightly oval in outline, and exhibits a clear boundiug- 

 wall differentiating it from the substance of the nucleolus. 

 Aqueous solution of logwood reveals its outline well, still 

 better is a solution of iodine ; but I prefer to either of these 

 a \ per cent, solution of eosin in common methylated spirit. 

 After verifying its apparent invariable presence in the 

 plant cell, a preparation of cerebellum, which I had made 

 in Professor Rutherford's class of Practical Physiology, 

 was submitted to the microscope. In the large multi- 

 polar nerve-cells a nucleolus has long been known to exist, 

 but inside many nucleoli this new structure was quite 

 visible. Dr Priestley informs me that it has been men- 

 tioned before casually, but no importance was attached to 

 it. On looking over various zoological works one finds that 

 it is figured repeatedly ; as to its presence in the animal 

 cell we may for the time neglect it. To this new factor 

 in the vegetable cell I propose applying the term nucleolo- 

 nucleus. JMy investigations led me strongly to the con- 

 clusion that the nucleolus is also an invariable element ; 

 in fact all the tissue systems of every plant, which have 

 come under my notice in the present connection, are pro- 

 vided invariably with a nucleus, nucleolus, and nucleolo- 



