1910.] Forms of Plants as a Result of Environment. 555 



capacity of all leaf-axils to produce new buds is only realised in experiments 

 in which either the Howering rosettes are continuously fed on inorganic 

 salts ov when the top of the inflorescence is cut off. In consequence of 

 this injury, new branches or single flowers are to be found on the whole 

 stem in the axils of all the leaves. The flowers appear also in the axils 

 of the old leaves of the rosette itself, when we extirpate the terminal bud of 

 a rosette, ripe to flower but not yet lengthened, and cultivate it in' strong 

 light. 



We have found that the terminal flower can be replaced by a leaf rosette 

 under the influence of darkness or blue light. From these facts we can 

 draw the conclusion that at all other places suitable for the genesis of flowers 

 rosettes can be caused quite as well. In all such cases we meet with a 

 certain difficulty due to the peculiar quality of plants known as polarity 

 from the researches of Vochting. On the stem of a potato plant we observe 

 that the different places produce different organs, as, for instance, on the 

 basal parts, colourless runners and later on potatoes, wliile from a higher 

 level of the foliage shoots or flowers arise. A similar phenomenon can be 

 observed with the stem of Sempervivum, whose basal parts have a tendency to 

 form rosettes, whilst the apical ones tend to form flowers. In opposition 

 to the ideas of Vochting, who ascribes the polarity to innate hereditary 

 causes, I assume that the external conditions at the different places of a 

 stem cause internal differences and thereby the formation of different 

 organs. 



At the basis near the soil the freer supply of water and nutritive salts 

 favour the formation of rosettes, whereas the apical parts more distant from 

 the soil, in drier air and receiving more light, give birth to the flowers. 



These views are verified by the fact that in the experiments rosettes can 

 arise anywhere in place of flowers. A plant, ripe to flower, but made 

 vegetative by blue light, when brought later on into an intense white light 

 forms rosettes in all leaf axils. Similar rosettes, continuously and vigorously 

 fed during the formation of the inflorescence, produce new rosettes at the 

 basal parts in the axils of the old leaf, after we have cut off the inflorescence. 

 But it is also possible to cause the formation of rosettes on the apical 

 branches, and, according to the state of the plant and the variously combined 

 influences, we succeed in obtaining manifold combinations of rosettes and 

 flowers on the same plant. 



Under ordinary circumstances the whole plant dies after the flowering 

 and the ripening of fruit. This natural death is not at all a consequence 

 of an innate necessity, but only follows from the reproduction taken in 

 connection with the limited nutrition. All the plants which were compelled 



