i8o The Anatomy of Plants BOOKII 



or a much-coiled fibre. In some part of the substance 

 conspicuous granules occur, one of which is usually very 

 conspicuous and constitutes the nucleolus. The network 

 or fibril is composed of a more or less homogeneous ground 

 substance, in which lie granules of a material that stains 

 easily with various dyes. Flemming called the staining 

 substance chromatin ; the non-staining achromatin ; Schwarz, 

 in 1887, called the non-staining basis of the reticulum in 

 which the chromatin is imbedded, linin. 



Further researches showed that the chromatin may be 

 present in the thread either in the form of granules, or as 

 a network embedded in the linin, the latter thus itself 

 forming an achromatic network intermingled with the 

 other. 



This conception of the structure underwent little change 

 till Heidenhain showed in 1893-4 that the achromatic net- 

 work is also granular in composition. He thus distin- 

 guished two kinds of granules in the linin thread : the first 

 known, which he called basichromatin, being associated with 

 the other, oxychromatin, in the staining portion, the oxy- 

 chromatin granules alone being present in the non-staining 

 portion of the linin. He used the names mentioned to 

 indicate differences of reaction to stains ; the basichromatin 

 granules taking up the basic tar-colours such as saffranin, 

 the oxy chromatin being stained by acid tar-colours like eosin. 



The ground substance of the nucleus was said by Reinke 

 in 1894 to consist of large pale granules of non-staining 

 material, to which he gave the name oedematin. 



The nucleus in the cell is delimited by a kind of mem- 

 brane, which according to Klein, who studied it in 1878, 

 is a denser portion of the cell protoplasm, much like the 

 limiting layer of the vacuole. Van Beneden endorsed this 

 view in 1883. 



The chemical substance of the nucleus was first investi- 

 gated by Miescher in 1871, when its great richness in 



