206 Mr J. M. Macfarlane on the 



obscured, owing to the rotundity of the cell, nucleus, and 

 nucleolus, but in the great majority of cells it is very 

 apparent, and attains a much larger size than in any 

 other plant, excepting Fritillaria, which has come under 

 my notice. 



Finally, I would speak of the result of staining agents 

 such as those already referred to. The whole of these, if 

 the solution be not too strong, stain the peripheral proto- 

 plasm scarcely at all ; the nuclear substance is slightly 

 stained, the nucleolus rapidly absorbs and soon assumes 

 a brilliant hue, while the nucleolo-nucleus has a deeper 

 tint imparted to it. The general character of these, in 

 fact, when treated chemically, lead to the conclusion that 

 each is a more richly differentiated mass of protoplasm 

 than that by which it is surrounded. 



2. Cell Division. — My study of cell division in S. nitida 

 has been carried on wholly by chromic acid preparations 

 slightly stained with heliocin. The material was obtained 

 in a state of division, by placing quantities of it in 1 per 

 cent, solution of chromic acid, during different hours of the 

 night, that gathered at 3 a.m. giving the best results. 



Taking as our starting-point a typical cell just initiating 

 the dividing process, the first change observable is the 

 aggregation, on two opposite sides of the nucleus, and 

 in a line with the long axis of the cell, of a quantity of 

 pale, slightly granular protoplasm, which seems to be 

 derived from the peripheral layer, and to travel along the 

 radiating threads, for during aggregation little masses can 

 be seen here and there along the course of the threads in 

 addition to that already massed. Coincident with this, or 

 soon thereafter, a very curious movement is set up in the 

 nucleolus, the exact course of which it is rather difficult to 

 follow ; one or two very clear preparations, however, made 

 by Mr Jackson, a senior member of the University Practical 

 Botany Class, as also several of my own, have helped me 

 to gain a definite idea of what now goes on.* The nucleolus 

 swells out on opposite sides into two protuberances, in 

 line with the aggregating protoplasm ; these do not seem to 



* I would here express my indebtedness to Mr Jackson for the use of about 

 two dozen slides — prepared in connection with the ckiss — of nuclei (^uite iso- 

 lated from their cells, and remarkably fine for exact definition. 



