26 



BOTANY OF THE LIVING PLANT 



of turgor ; for upon it depends that crispness of succulent parts, 

 which they lose on wilting or withering. The relation of the turgescent 

 cytoplasm and the resistant cell-wall is like that of the bladder and 

 skin of a football, or of the inner and outer tubes of a pneumatic 

 tyre. When these are inflated they are firm and rigid ; when deflated 

 they are flaccid and limp. So it is with the plant-cells. But here 

 It is fluid, not gaseous pressure. The effect of a fall in pressure is 

 seen in any wilting plant. Withering is the result of the water-supply 

 being insufficient to secure the turgor of the cells. If sufficient water 



Fig. 15. 



Cells from the prothallus of Nephrodium viUosum after treatment with 3 per cent, 

 solution of conmion salt ( x 550). Drawn as observed about 15 nrinutes after plasmo- 

 lysis ; the threads are very fine, but appear proportionally thicker in the figure than 

 tliey actually are. 



be supplied to the still living cells of a wilted plant, their turgor 

 will be resumed, and it will recover its firmness. Similarly, the 

 artificially plasmolysed cell loses its mechanical firmness, like a 

 deflated tyre ; but may resume it when the plasmolysing salt is 

 washed away, provided that the cell still maintains its life. 



The relation of the cell-wall to the cytoplasm is not a mere 

 juxtaposition of two quite distinct things, like the bladder and skin 

 of a football. That their connection is more intimate is shown by 

 the fact that on plasmolysis being carried out carefully and slowly, 

 fine threads of cytoplasm may be seen to stretch from the wall to 

 the contracted mass (Fig. 15). This indicates an intimate relation. 



