in Plant Cytology. 189 



period, it persists for a considerable time as a spherical blad- 

 der, surrounded by a delicate protoplasmic sheath, and con- 

 nected by refractive threads with the nucleolus internally, and 

 by the radiating strands externally, while definite pores in it 

 permit the outflow of the nucleoplasm. In other plants most 

 observers describe its gradual absorption during the middle, 

 or later prophase stages. This is clearly seen in dividing 

 bean, corn and banana cells. The aggregating constituents 

 of it, which have been stained by iron-haematoxylin and 

 Bordeau red, indicate a linin and chromatin combination. In 

 daughter cells which are passing from the anaphase to the 

 telophase state, the nuclear membrane differentiates first round 

 the outer ends of the poles, and gradually grows round the 

 nuclear substance. This differentiation is contemporaneous 

 with redistribution of the linin and chromatic substance, and 

 reformation of the nucleolus. The recent statements by 

 Wisselingh that the nuclear membrane, network, and nucleo- 

 lus undergo varying degrees of corrosion, suggest specific 

 physical or chemical differences, the exact value of which we 

 cannot as yet estimate. 



Nuclear Substance. — If we exclude the nucleolus, the 

 nuclear substance with its membrane make up the bulk of the 

 nucleus. Many histologists now distinguish three components 

 in it, the nucleoplasm, the network or linin substance, and the 

 deeply-stained granules or chromatin. Appealing again to 

 dividing cells, the role of events consists in the aggregation 

 of refractive substance of the nuclear membrane and still 

 earlier of the network, and, as is being more and more fully 

 recognized, with distribution in most cells of the nucleolar 

 substance. When preparations are even slightly over-stained 

 the aggregating substance is uniformly dense, but a proper 

 degree of staining reveals that the aggregating loops or 

 threads are made up of more deeply-stained bodies, the chro- 

 matin granules, as described by Debski and others, which are 



