8 THE CAUSES OF FLUCTUATIONS IN TUKGESCENCE 



which the sparsely distributed stoniata are present. Only a little watery fluid had 

 escaped at this time, and that solely from the cut extremity of the shoot. On the 

 following morning the uncut surfaces were universally coated by a dry, readily detached, 



o -*«*—© 



ance 



chalky white layer of concrete latex. Very little watery cell-sap could have escaped, 

 as, even after the dry latex had all been carefully rubbed off, the shoot showed* 

 a loss of only 0-41 grammes in weight. The cut surface of the pith was, however, 

 slightly depressed, and any section or slight pressure of the epidermis of the intact 

 surfaces was followed by abundant exudation of clear fluid. Microscopical sections of the 

 tissues showed the ramified milk tubes in a more or less shrunken condition, with 

 their walls often thrown into longitudinal wrinkles, giving them a finely striate appear- 

 and their abundantly nucleated protoplasmic lining contracted. The wrinkling 

 of the tubes and the recession of the protoplasm from the walls are phenomena 

 which are no doubt to be ascribed to the action of the reagents employed in staining 

 and mounting the preparations; but the entire results of the experiment clearly show 

 that the high state of turgescence normally present in the laticiferous system in such 

 cases is no mere passive engorgement due to extraneous pressure exerted by surrounding 

 turgid tissue elements, as Sachs seems to imply.* For, were it due to any such agency, 

 exposure to anaesthetic influences ought certainly not to have given rise to any exuda- 

 tion of latex, seeing that its tendency is to give rise to diminished turgescence generally, 

 and therefore to diminished pressure on the milk tubes. The fact that the tubes are 



g 



provided with a continuous protoplasmic lining (plate III. fig. 1) is in itself sufficient to 

 indicate that the conditions of turgescence within them must be influenced by intrinsic 



and the fact that exudation of latex precedes that of exudation of cell-sap would 

 appear to imply that such agencies are really the main determinant of the extremely 

 high turgescence which normally prevails. What would appear to be the only satisfactory 

 planation of the phenomena is that both the laticiferous tubes and the other living 



iscence, but that the turgidity in the former 



elements are in a state of 



o 



is higher than that in the latter, so that, on the general depression of functional activity 

 incident on the action of an anaesthetic, latex escapes more quickly than common cell-sap, 

 and, occupying the intercellular spaces and concreting when it escapes from the stomatic 

 orifices, prevents the free exudation of the latter. The results of the experiment further 

 show that, in any continuous system of tubes of this nature, turgescence must be inter- 

 rupted at any points where the functional activity of the protoplasm has been depressed 

 or abolished, such points constituting sites of localised leakage from the system. 



In the case of tissues like those employed in the above experiments, the demonstra- 

 tion of the difference between mere saturation and turgescence is rendered particularly 

 plain, owing to the abundant free exudation of fluid which accompanies anaesthesia ; but 

 aimost equally striking demonstrations are forthcoming in cases where we employ tissue- 

 in which the cell-sap contains coloured matters in solution, as the escape of these from the 

 interior of the cell-cavities gives rise to striking changes in appearance, especially in the 

 case of parti-coloured leaves, such as those of many Begonias, &c. 



The following experiments illustrate the nature of the phenomena in such cases: 



Experiment /.— A leaf of Begonia rex, weighing 1*44 grammes, was set in a chloro- 

 form-chamber. The upper surface of the leaf was dull green at the margins and centre 



_ _ _ 



* Vorlesnng, XI. s. 206. 



