ng", I. II. "Centralbl." 1904.)

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.
(Cf. numerous records of this kind by Diels, "Jugendformen und Bluten",
Berlin, 1906.) This shortening of the period of development is exhibited
in the most striking form in trees, as in the oak (Mobius, "Beitrage zur
Lehre von der Fortpflanzung", Jena, 1897, page 89.), 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. (Klebs, "Willkurliche Aenderungen", etc. Jena,
1903, page 130.) Theoretically, however, experiments are of greater
importance in which the production of flowers is inhibited by
very favourable conditions of nutrition (Klebs, "Ueber kunstliche
Metamorphosen", Stuttgart, 1906, page 115) ("Abh. Naturf. Ges. Halle",
XXV.) 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, however, 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 cases 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 carbohydra