CHANGING OF SPECIES. 



11 



is that both fungi and the higher plants are, if in full vigour, able 

 immediately to adapt themselves to changed conditions. 



The weapons on both sides are excretions of some kind. A new 

 and hitherto unexperienced poison seems to be at once countered 

 by the defender producing a novel anti-body. If this is a correct descrip- 

 tion of what happens, then undoubtedly vegetable protoplasm has the 

 power of adapting itself to a new environment. 



The flowering plants are, of course, infinitely more difficult to 

 change than unicellular organisms or fungi. Still there are cases 

 admitted by most botanists and which seem conclusive enough. 



Changes are certainly brought about by a difference in the salts 

 in solution absorbed by the roots. 



The special races which occur on limestone and on serpentine are 

 well known and have been fully discussed by many authorities, and 

 it is hardly necessary to refer to them. But certain experiments with 

 solutions of common salt are perhaps of more interest in this connexion. 



It has been found that wallflowers when watered with salt solution 

 are distinctly changed. Their leaves become fleshy, or, as one might 

 say, halophytic. This expedient is not new, but has recently been 

 confirmed by Boodle.'^ The power of adaptation to various concentra- 

 tions of salt has been directly studied both by Terras! and Hill.| 

 The former had managed to accustom the root-hairs of a Salicornia to 

 live in a solution of 5.8 per cent, of common salt. It was then placed 

 for two hours in a 1 per cent, solution, but when it was again placed 

 in a 5.8 per cent, solution, the protoplasm of the root hairs was at once 

 plasmolysed. 



Nor are these the only instances which could be mentioned of 

 this power of adaptation in direct response to change in the constitution 

 of the root water. 



Ordinary seeds will not germinate in salt water, and yet the seeds 

 of some salt plants will only germinate in salt water. 



The orchid Laelia vurpurata is another curious instance for, 

 according to Noel Bernard, § the seeds can develop only if a special 

 fungus is present. 



Some of those who have recently studied the flora of peat mosses seem 

 to think that there is a peculiar substance, probably an enzyme, present 

 in all peaty soils, and that is the reason why the flora is so scanty 

 (Dachnowsky). II Only those plants which can manage to adapt 

 themselves to this particular substance are able to survive in such soils. 



There are also certain direct experiments which show that there is 

 a possibility of altering the constitution of plants by altering the com- 

 position of the water supplied to the roots. 



Masses (as described in our Society's Journal vol. 28) was able to 

 obtain races of both Cucumber and Tomato which were immune io 



* Boodle, New Phytologist, 1904. 



+ Terras, Proc. Scot. Micr. Soc.y vol. iv. 



X Hill, New Phytologi&t, vii. 1908. 



§ Noel Bernard, Com'ptes Rend. 1903. 



II Dachnowsky, Botan. Gazette, xlvi. Aug. 1908. 



