TKANSACTIOSS OF SECTION D. 761 



7. Experimental Observations on the Function of the Nucleus in the Vege~ 

 table Cell. By Jas. Clark, M.A., Fh.D. 



"When certain cells are immersed in a 10 to 20 per cent, solution of cane sugar 

 a plasmolytic shrinking takes place in the protoplasmic contents, and it often 

 becomes possible with careful manipulation to strip away the cell wall and leave 

 the rest of the cell intact. When this has been done in the case of Spiroc/yra and 

 Nitella, and of cells from the leaf of Fimaria Jiygrometrica, Elodea cmiadensis, and 

 Tallisneria spiralis, a new cell wall as a rule appears. "When the nucleus is 

 eccentric the new cell wall makes its first appearance in the proximity of the 

 nucleus and gradually spreads over the whole of the protoplast. In Spirogyra, 

 for instance, if the nucleus be in the centre of the cell, the new cell wall first 

 appears as a girdle round the middle of the somewhat elongated protoplast ; if the 

 nucleus be at the side, then cell-wall formation begins as a rule at that point on 

 tlie outer surface of the protoplasm nearest the nucleus, and for a variable time 

 cell-wall formation is confined to that side of the protoplast where the nucleus 

 happens to be. 



Slight mechanical irritation of the protoplast in Spirogyra at a point near the 

 nucleus hastened the formation of the cell wall ; or, if the cell-wall formation had 

 already begun, caused an increasing thickness in the same. Similar irritation at a 

 point remote from the nucleus caused protoplasmic contraction and reduction in 

 the complexity of the protoplasmic movements in the neighbourhood. 



By purely mechanical means it is possible, by compressing the cell wall, to 

 divide the contents of a cell of Spirogyra and various other plants into two equal 

 parts completely separated from each other, the one half containing the nucleus, 

 the other not. The part containing the nucleus functionates exactly as an 

 ordinary cell, but is, if anything, more active. In the case of Spirogyra it can 

 form a new cell wall, and many, by repeated cell division, grow into" a new and 

 independent filament, provided the old cell wall be torn to allow its escape. When 

 submitted to slight mechanical irritation the nucleated portion usually passes into 

 a resting stage. In Spirogyra the part without the nucleus is capable of forming 

 starch, occasionally in abundance ; and the protoplasmic movements usually 

 undergo extensive simplification, well-marked circulation being at times converted 

 into rotation. When protoplasmic movements are arrested in the non-nucleated 

 portion by the withdrawal of oxygen, they are not restored by the introduction of a 

 normal oxygen supply. 



When the tip of a very young root-hair of Trianea hoyotensis is separated from 

 the basal nucleated portion the nucleus advances towards the place of separation, 

 where the formation of a new layer of cell wall occurs. The nucleus then returns 

 to its original position and the hair resumes ordinary growth. In a hair so 

 treated the characteristic fountain-like rotation never subsequently appears, though 

 in other respects the hair may be quite normal. 



8. Co-ordination of Cellular Oroivth and Action by Physical Forces. 

 By Francis "Waenek, M.D. 



Referring to former publications, the author points out the importance of 

 studying cellular action, and the attributes, time, and quantity of action, in each 

 elemental part of the object observed ; this is particularly needful in studying the 

 brain. Generalisations from observation of cellular growth are formulated, with 

 references to examples of control by physical forces. Co-ordination of growth and 

 of nerve-action is alike due to control of the attributes (time and quantity) of the 

 elemental parts of the organism, leading to proportion and form of growth, and 

 order of nerve-action ; both supply of pabulum and stimulation may bring about 

 such co-ordination. 



In children normal proportional growth and normal nerve-action have been 

 shown usually to coincide. 



Evidence is advanced that ' similar living things under similar conditions of 



