54 SUCCULENT PLANTS [CHAP. 



is, at least, a potent cause in its production. 

 He succeeded in making plants, such as garden- 

 cress, succulent, by watering them with salt 

 water this of course is a motive for salting 

 asparagus beds. He also testifies to the 

 hereditary effects, in that plants raised from 

 seed, obtained from plants of cress, which were 

 somewhat succulent in the first year's experi- 

 ment, became still more so in the following; so 

 that an increment was added in the second 

 year to the hereditary succulency of the first 

 generation. 



" From all the above facts, natural and experi- 

 mental, the conclusion is inevitable, that while 

 succulency is of benefit to the plants under the 

 conditions in which they naturally grow, it is 

 in all cases actually brought about by the direct 

 action of the environment itself, coupled with 

 the responsiveness of the protoplasm of the plant. 

 It then becomes hereditary." 



There are great differences in the plasticity of 

 succulent plants. In the above I have given 

 instances of easy transitions from thick to 

 thin leaves or vice versa ; but plants grown 

 from "time immemorial" under natural xero- 

 phytic conditions now resist the direct action 

 of changed conditions ; so that species of 

 Mesembryanthemum, Crassula, etc., etc., still 

 retain their succulency under cultivation in this 

 climate, though raised from seed. 



There is a remarkable tenacity of life in these 



