340 



experiments with Helianihus annuus Vochting found little tubercles formed 

 on the roots. I observed barrel-like thickenings of the sharply bent roots 

 of sweet cherries. 



The swellings, described by Warburg' in the branch canker of the kina 

 tree on damp soils, may also represent such correlation phenomena. 



Retrogrkssive Metamorphosis (Phyllody). 



If the organs of a morphologically higher developmental stage seem 

 transformed into those of a lower one, we speak of a retrogressive meta- 

 morphosis. The change in the blossoming organs is pathologically of mo- 

 ment only if the sexual apparatus, by changing into a group of vegetative 

 organs, loses the purpose for which it was designed and thereby initiates 

 sterility. 



These cases are listed under the group of phenomena caused by excess 

 of water and nutriment, in accordance with the following theory. The 

 development of the vegetable organism depends upon two factors, the con- 

 stitution of the organic building materials and the way in which they are 

 utilized. With the assumption that the first achievement of the organism, — 

 assimilation, i. e., the formation of new dry substance, — takes place in a 

 normal way, the development of the plant depends upon the way in which 

 this organic building material is utilized. In this we recognize two directions 

 which we will keep separate as the vegetative and the sexual generations. 

 The latter is initiated usually by the appearance in the organism of an often 

 clearly recognizable dormant period in the production of its vegetative 

 apparatus. As a rule, new leaves are not formed at this time, the apical 

 growth of the twigs stops. In place of this the process of the storage of 

 reserve building material becomes conspicuous. 



We find this storage process initiated and favored by a decrease in 

 the absorption of water with increasing light and heat. An increased con- 

 centration of the cell sap is required, if the reserve substances, for ex- 

 ample, are deposited in the form of starch. If such a concentration cannot 

 be obtained under any circumstances whatever and the building substances 

 remain in a diluted form, — for example, sugar, — only a slight impetus is 

 necessary to start up vegetative activity. Thus, a certain antagonism pre- 

 vails between the two developmental phases, which we may consider as 

 transmissable adaptations to atmospheric conditions. After a cool wet 

 period when the plant takes mineral substances from the soil and through 

 the production of the leaves causes the chlorophyll apparatus to attain to 

 its richest possible development, a warmer, drier period follows which 

 makes possible the greatest amount of light. In this period the sexual 

 organs are formed from the finished, plastic building materials prepared 

 in the leaves and develop further, after a shorter or longer dormant period. 



1 Warburg-, O., Beitra^ zur Kenntnis ties Krebses der Kinabaume auf Java. 

 Cit. Bot. Centralbl. 1888. Vol. XXXVI, p. 145. 



