170 



SCIENCE 



[N. S. Vol. XXXIII. No. 840 



parent plants of which certainly exhibited no 

 striking abnormalities. In a short time many 

 hitherto latent potentialities became apparent, so 

 that characters, never previously observed, or at 

 least very rarely, were exhibited, such as scattered 

 leaf arrangements, torsion, terminal or branched 

 inflorescences, the conversion of the inflorescence 

 into foliage-shoots, every conceivable alteration 

 in the color of flowers, the proliferation of flowers. 



One more quotation will sufficej this time 

 from Bailey.*^ 



Now let us endeavor to put ourselves in na- 

 ture's place, if such a conception is possible, and 

 to briefly follow an outline of her methods with 

 plants. We shall find that variation is largely 

 the result, so far as we can see, of excess of 

 food supply. The seedsman knows that heavy 

 lands make his seed-crops break into non-typical 

 forms, and he therefore prefers, for most plants, 

 a soil not very rich in nitrogen or growth pro- 

 duction. Heavy soils make the dwarf peas 

 " viney," and bud sprouts of curious leaves and 

 flowers are wont to appear upon over vigorous 

 shoots. 



Since conditions which tend to shorten 

 the life of a plant or tree often cause the 

 plant or tree to flower,*- it follows that 

 conditions which favor a rank growth are 

 likely to be disadvantageous to the pro- 

 duction of flowers. This is actually the 

 case.*^ 



One extreme case, that of exceptionally early 

 flowering, has been observed in nature and more 

 often in cultivation. A number of plants under 

 certain conditions are able to flower soon after 

 germination. This shortening of the period of 

 development is exhibited in the most striking 

 form in trees, as in the oak,*' flowering seedlings 

 of which have been observed from one to three 

 years old, whereas normally the tree does not 

 flower until it is sixty or eighty years old. 



Another extreme case is represented by pro- 

 longed vegetative growth leading to the complete 



" " The Survival of the Unlike," 169, 1898. 



•" iVlobius, " Beitrage zur Lehre von der Fort- 

 pflanzung der Gewachse," 7, 125, 1897. 



"Klebs, "Darwin and Modern Science," 232, 

 246, 1909. 



" Mobius, " Beitrage zur Lehre von der Fort- 

 pflanzung der Gewachse," 89, 1897. [The condi- 

 tions are not given by Mobius. — W. D. B.] 



suppression of flower-production. The result may 

 be obtained with several plants, such as Glechoma, 

 the sugar beet. Digitalis, and others, if they are 

 kept during the winter in a warm, damp atmos- 

 phere, and in rich soil; in the following spring or 

 summer they fail to flower. Theoretically, how- 

 ever, experiments are of greater importance in 

 which the production of flowers is inhibited by 

 very favorable conditions of nutrition occurring 

 at the normal flowering period. Even in the case 

 of plants of Sempervivum several years old, 

 which, as is shown by control experiments on 

 precisely similar plants, are on the point of 

 flowering, flowering is rendered impossible if they 

 are forced to very vigorous growth by an abun- 

 dant supply of water and salts in the springs. 

 Flowering, however, occurs, if such plants are 

 cultivated in relatively dry soil and in the pres- 

 ence of strong light. Careful researches into the 

 conditions of gro^vth have led, in the case of 

 Sempervivum, to the following results : ( 1 ) With 

 a strong light and vigorous carbon assimilation 

 in strong light, a considerably increased supply of 

 water and nutritive salts produces active vege- 

 tative growth. (2) With vigorous carbon as- 

 similation in strong light, and a decrease in the 

 supply of water and salts, active flower produc- 

 tion is induced. (3) If an average supply of 

 water and salts is given, both processes are pos- 

 sible; the intensity of carbon assimilation deter- 

 mines which of the two is manifested. A diminu- 

 tion in the production of organic substances, par- 

 ticularly of carbohydrates, inauces vegetative 

 growth. This can be effected by culture in feeble 

 light or in light deprived of the yellow-red ray: 

 on the other hand, flower-production follows in- 

 crease in light intensity. These results are essen- 

 tially in agreement with well-known observations 

 on cultivated plants, according to which, the ap- 

 plication of much moisture, after a plentiful 

 supply of manure composed of inorganic salts, 

 hinders the flower-production of many vegetables, 

 while a decrease in the supply of water and salts 

 favors flowering. 



Good manuring is in the highest degree favor- 

 able to vegetative growth, but is in no way 

 equally favorable to the formation of flowers. 

 The constantly repeated expression, good or favor- 

 able nourishment, is not only vague but mislead- 

 ing, because circumstances favorable to groivth 

 differ from those which promote reproduction; 

 for the production of every form there are certain 

 favorable conditions of nourishment, which may 

 be defined for each species. Experience shows 



