341 



The more the plastic material is worked up by the leaves, the more 

 numerous and perfect are the sexual organs formed within this dormant 

 period. The manner in which these primordial buds subsequently develop 

 depends on the nature of their further nourishment. If influences make 

 themselves felt which are necessary for the maturing of the vegetative 

 organs, foliage leaves will develop and, indeed, either from the newly 

 formed centres or from the already existing primordia of the sexual gene- 

 ration. Thus "phyllody" takes place. 



From our experience in horticulture, we know that an abundant supply 

 of nutritive substances with a simultaneous increase in warmth and mois- 

 ture, usually at the time of a lesser light action, are conditions initiating 

 and favoring the process of phyllody. This becomes especially apparent 

 in the production of double flowers, in which the stamens are transformed 

 into petals. 



Since this process can become hereditary, like all changes in the di- 

 rection of growth, where conditions remain equal, and may be increased, 

 it is evident that we will find examples in which the tendency to the retro- 

 gression of the sexual organs into forms of morphologically lower develop- 

 ment, has afi'ected all parts of a flower, and then the whole blossom turns 

 green. 



Of course, the influence of the soil is rarely the direct cause of phyllody. 

 This is due rather to definite combinations of all the factors of growth, as 

 already mentioned, and also occurs not infrequently as a correlation phe- 

 nomenon resulting from the suppression of other processes of growth. Thus 

 phyllody of individual flowers and inflorescences is produced by injuries 

 to the vegetative axis and by vegetable and animal attacks (mites). For 

 example, C. Kraus^ removed leaves from H elianthus annuus plants of differ- 

 ent ages, leaving only the bracts of the blossom head. In the older plants 

 the bracts curled back and enlarged prematurely. In the younger plants 

 25 per cent, showed an actual phyllody; since the bracts assumed, more or 

 less, the form of foliage leaves. 



In my freezing experiments, I have often observed that the bud scales 

 were transformed into herbaceous, leaf-like organs after the apical portion 

 had been destroyed by frost. Goebel- obtained similar results by removing 

 the leaves of young plants of Prunus Padus, Aesculus, Rosa, Syringa and 

 Quercus, and then putting the plants into plaster casts. 



Teratology has classified the phenomena. The simplest case is 

 "virescence," turning green, in which an organ of the flower retains its 

 form in all essentials, but becomes green in color. As a rule, the organ be- 

 comes fleshier with this appearance of the chlorophyll coloring matter. In 

 the actual metamorphosis of the floral organs into leaves (phyllody, phyl- 



1 Kraus, C, Untersuchungen tiber kiinstliche Herbeifuhrung der Veiiaubung 

 usw. durch abnorme Drucksteigerung. Forsch. auf. d. Geb. d. Agrikulturphysik. 

 ]880, p. 32. 



2 Goebel, Beitrag-e zur Morphologie und Physiologie des Blattes. Bot. Zeit. 

 1880, p. 803. 



