SIGNIFICANCE OF MALFORMATIONS 181 



I to recount here the hypotheses which have been built upon these 

 abnormalities, as experience shows that the history of development; and 

 not these hypotheses, has given us the explanation of the relationships of 

 configuration of the stamen. There can be no doubt to the unprejudiced 

 eye that the stamen of an Angiosperm is homologous with that of a 

 Gymnosperm. The theories of malformation however which were framed 

 for the Angiosperms could find no application in the Gymnosperms. 

 But I cannot go further into this matter here. With reference to 

 the phyllody of stamens I have only further to say, that of course the 

 possibility of the transformation of the primordium of a stamen into the 

 lamina of a simple foliage-leaf or of a petal must have existed longer 

 in those plants in which the pollen-mother-cells are only formed at a 

 relatively late stage of development than in those which lay down the 

 archesporium at a relatively early period. In considering then the trans- 

 formation of the primordia of stamens we have to regard first of all the 

 stage of development of the primordiitm at the moment when the impulse 

 to the transformation, if such an expression may be allowed, was received, 

 and also the strength of this impulse, for this it is which determines 

 whether we obtain a simple or a four- winged foliage-leaf or petal, or such 

 a leaf with more or less malformed pollen-sacs distorted at their insertion. 



In even greater degree than the phyllody of stamens has the phyllody 

 of ovules given rise to morphological hypotheses. The facts are shortly 

 as follows : 



On cultivated plants especially one not infrequently finds flowers 

 altered by disease in which a portion or all of the leaf-organs have the 

 form of foliage-leaves. This is the case, for example, in Aquilegia vulgaris, 

 Reseda odorata, Alliaria officinalis, and others. The cause of this phyllody 

 is mostly unknown. In some cases, as Peyritsch has experimentally 

 shown, it is induced by insects ; in others we may assume that the sexual 

 potency has been enfeebled whilst the vegetative has been increased 

 through the nutritive conditions. In flowers which exhibit this phyllody 

 the carpels especially are more or less changed ; they are either only 

 enlarged and inflated, or in the place of each carpel a foliage-leaf appears 

 as is so common in Tiifolium repens and in other cases, such as the 

 double cherry. When such complete phyllody of the carpels occurs there 

 are usually no ovules ; their formation is entirely suppressed. In flowers 

 of Alliaria officinalis, for example, when the most complete phyllody is 

 exhibited we find the sepals, stamens, and carpels, completely transformed 

 into foliage-leaves with buds and shoots in their axils, and the carpels 

 show no trace of ovules. The influence which caused the phyllody of 

 the primordia of the leaves in the flower-bud has here made itself felt 

 even before the ovules \\ere laid down. In less perfect cases of phyllody 

 formations are found in the carpels which are evidently the product of 



