232 Influence of Environment on Planis 
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 prolonged vegetative 
growth leading to the complete suppression of flower-production. 
This 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 atmosphere, and in rich soil; in the following 
spring or summer they fail to flower®. Theoretically, however, experi- 
ments are of greater importance in which the production of flowers is 
inhibited by very favourable 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 
abundant supply of water and salts in the spring. Flowering, how- 
ever, occurs, if such plants are cultivated in relatively dry sandy soil 
and in the presence of strong light. Careful researches into the 
conditions of growth have led, in the case of Sempervivum, to the 
following results: (1) With a strong light and vigorous carbon- 
assimilation a considerably increased supply of water and nutritive 
salts produces active vegetative growth. (2) With a vigorous carbon- 
assimilation in strong light, and a decrease in the supply of water and 
salts active flower-production is induced. (3) If an average supply 
of water and salts is given both processes are possible; the intensity 
of carbon-assimilation determines which of the two is manifested, 
A diminution in the production of organic substances, particularly of 
carbohydrates, induces vegetative growth. This can be effected by 
culture in feeble light or in light deprived of the yellow-red rays: 
on the other hand, flower-production follows an increase in light- 
intensity. These results are essentially in agreement with well- 
known observations on cultivated plants, according to which, the 
application 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 favours 
flowering. 
! Cf. numerous records of this kind by Diels, Jugendformen und Bliten, Berlin, 1906. 
2 Mobius, Beitriige zur Lehre von der Fortpflanzung, Jena, 1897, p. 89. 
3 Klebs, Willkiirliche Aenderungen, etc. Jena, 1903, p. 130. 
4 Klebs, Ueber ktinstliche Metamorphosen, Stuttgart, 1906, p. 115 (4bh. Naturf. Ges. 
Halle, xxv.). 
