346 



only a metamorphosis of scattered buds into leaves, but that a very local 

 affection of the cells of some buds is present, this does not upset at all 

 our theory of phyllody. It is a matter of course that the formation of each 

 organ takes place under definite nutritive conditions. That these change 

 constantly and are the product of the momentary combination of all the 

 factors of growth has been emphasized already in the introductory chapters 

 of this edition. It is still far from possible to determine these combinations. 

 .For the present, we have only scattered observations on this subject,— that, 

 for example, an excess of potassium and nitrogen in relation to the con- 

 sumption of the other nutritive substances one-sidedly increases the vege- 

 tative activity at the expense of the sexual development. An excess of 

 water with a relatively scanty supply of light can in a similar way influence 

 the direction of growth. We cannot determine how these disturbances in 

 equilibrium are produced individually for the formation of each organ, 

 whether momentary arrestments in the absorption or transportation of the 

 nutritive substances form the cause. 



We can, therefore, state only very generally that phyllody is produced 

 by a preponderance of the direction of growth producing green leaves as 

 against the mode of growth favoring the sexual organs. The so-called 

 "changelings" or spurious forkings, are plants which are still partially 

 fruitful. Among the conditions favoring the tendency to phyllody, Kaserer 

 cites unfavorable positions on which drainage water collects from higher 

 lying ground. Healthy plants set out in a group of affected plants are said 

 to fork rapidly. Superphosphate seems to favor a return to fruitfulness. 



We consider the replacement of diseased plants by healthy ones of 

 varieties which withstand a more abundant supply of water and heavier 

 soils to be the most advisable mode of procedure. The so-called aggregations 

 of forked plants might be improved by drainage and the addition of sand 

 together with that of calcium phosphate. 



Falling of the Leaves. 



The falling of the leaves, the normal result of age^ is of pathological 

 significance only because, under certain circumstances, it can appear 

 prematurely. - . 



The causes which may lead to such premature dropping of organs 

 are of different kinds, and extremes of weather may give rise to it. Ac- 

 cordingly, the phenomena could be treated in different sections of this book. 

 Nevertheless, we prefer to consider here the processes of loosening as a 

 whole, because they are connected with changes in the tissues, in which in- 

 creases of turgor occur decisively, after the organs, for any cause whatever, 

 have become functionally weak. In regard to the falling of the leaves, for 

 example, Wiesner- differentiates the falling of the leaves into a summer 



1 Dingier, H., Versuche und Gedanken zum herbstlichen Laubfall. Ber. d. 

 Deutschen Bot. Ges. VoL XXIII (1905), p. 463. 



-' Wiesner, Jul., Ber. d. Deutschen Bot. Ges. Vol. XXII (1904), p. 64, 316, 501. 

 Vol. XXIII. p. 49. 



