ADAPTIVE VAEIATIONS. 377 



Moreover these modifications were uniform, affected 

 all the tissues, and were rapidly produced, a week or 

 two sufficing. 



There is no evidence, as far as I am aware, to show 

 how widespread is this phenomenon of interchange be- 

 tween roots and stems, and hence one cannot accept it 

 as a generalised property of plants. In any case one 

 must bear in mind that it may not, after all, be a case 

 of direct adaptation to surroundings in the ordinary 

 acceptation of the term, but may be the calling up, in 

 response to one of two stimuli, of one of two groups of 

 characters long since acquired by the plant protoplasm. 



A case of adaptation which appeared to be to some 

 extent hereditary has recently been recorded by 

 Errera.* Conidia of the mould Aspergillus niger were 

 cultivated by Dr. Hunger for two generations in Rau- 

 lin's nutritive solution, to which 6 per cent, of common 

 salt had been added, and when placed in a similar salt 

 solution they were found to produce spores in 3f days. 

 Conidia which had been cultivated in the salt Raulin 

 solution for only one generation took 4 days to produce 

 spores, however, whilst those which had been culti- 

 vated in Raulin solution containing no additional salt 

 took 5 days. On the other hand, when some of the 

 conidia cultivated under the three sets of conditions 

 were placed in ordinary Raulin solution, those kept two 

 generations in salt solution showed only slight sporifi- 

 cation in 5 days, those kept one generation showed 

 more marked sporification, whilst those kept through- 

 out in ordinary Raulin solution spored in 4 days. 

 Spores from these three last cultures in normal Raulin 

 *Bull. Acad. Roy. Beligque, p. 81, 1899. 



