EVOLUTION AND ADAPTATION. 161 



it is the changed conditions of life which first stimulate the organism to 

 vary; the hereditary feral constancy is "broken," and then responsive 

 action on the part of the being follows. There is every reason to believe 

 that this is what took place with De Vries' mutations. Oenothera 

 Lamar ckiana had long been cultivated, and the plants dealt with had 

 first escaped from some garden into a field, there experiencing two 

 different environments. He then transferred them to a third, his own 

 garden, planting them in a manured border. There is nothing surprising 

 in their variations appearing under the circumstances. 



Nature is perpetually making analogous experiments. Thus ordinary 

 land plants often grow near to, and then in, the water ; e.g. Cardamine 

 pratensis, Bidens cernua, grasses, Ranunculus reperis, &c. Then the 

 usual adaptations to water at once appear. 



To make these hereditary the seeds must be sown for several genera- 

 tions in water. How long is not known ; but the dissected, submerged, 

 leaf of the water crowfoot is hereditary now, for it is retained on plants 

 raised from seed in a dried-up pond or in the garden. Many amphibious 

 plants in a similar manner change. 



Such and many other cases are illustrative of responsive changes in 

 the organism, which adapt it to a new environment. Of such, the author 

 says, "few as the facts are, they require very careful consideration," &c. 

 (p. 319). He betrays here a want of knowledge, as far as plants are 

 concerned. I accumulated many in my book,* published in 1895, and 

 can now add very many more. Dr. Morgan says " that the effects of 

 climate and food are only transitory factors." I am afraid it is quite the 

 reverse. The effects depend entirely on the length of time the organisms 

 have been subjected to them. M. Bonnier, in a recent paper on " Les 

 Plantes du Plateau des Nilghirris,"t has described how European plants 

 become changed and adapted to the new climate after some years ; but 

 those renewed every year by European seed never change, as they have 

 no time to do so. 



Dr. Morgan thinks that inheritance acquired by long-continued action 

 of the environment "is not likely to commend itself," and "there is no 

 evidence in support of it" (p. 338). 



The evidence is, in fact, abundant, both inductive and experimental. 

 Arguing against "adaptation," he says, if Nageli were right, "all 

 organisms living under the same conditions should show the same 

 characters " (p. 331). 



He seems here to betray an unfamiliarity with nature. As a matter 

 of fact, all plants do so in the general way of having xerophytic characters 

 under drought and hydrophytic in water, &c. But the different kinds of 

 structure adopted by plants are very various. Some are conspicuous by 

 spinescence and hard wood, others by succulency, almost devoid of all 

 woody tissues ; others are hairy or woolly, while some are glabrous but 

 with coriaceous foliage ; such and many other types are xerophytic. 

 He adds, " there are to be found as many exceptions as conformations to 

 the rule." I have not found it so, but among the five hundred or more 

 species of heath in Cape Colony I discovered one of a totally different 



* Origin of Plant Structures. 



f Rev. Gen. de Bot. vol. xvii. p. 289. 



M 



