MALFORMATIONS AND FORMATION OF ORGANS 201 



form l ' which has special bearings upon malformation. Sachs pro- 

 ceeds from the proposition that the differences in form of the organs of 

 plants are based on their material differences, and that the changes 

 of organic form are in touch with changes in the processes of nutrition. 

 The substances which cause the formation of a foliage-leaf are then 

 different from those required for the formation of an ovule, of a root, 

 and so forth. If this be the case, then the so-called ' morphological pro- 

 cesses ' are causal, just as this is true of, for example, the morphology 

 of a crystal, and we can picture to ourselves how it comes about that in 

 malformation one organ so frequently appears in place of another organ, 

 or that the relationships of form of the two kinds of organs are mixed up 

 together in the most different ways, even as the peculiarities of two species 

 are combined in their hybrid ; such intermediate formations are the 

 result of the wandering into the primordium of one organ of the material 

 which belongs to the formation of another. 



The malformations caused by insects show us that the formation of 

 organs is changed through material influences, although of course the 

 changes are determined by the peculiarities of the plant. Why malforma- 

 tions occur so abundantly in the flower whilst they are comparatively rare, 

 for example, in roots, may find its explanation in the following 2 : 



1. The primordia of organs arise at the vegetative point of the flower 

 rapidly after one another and commonly in great numbers closely over 

 and beside one another. 



2. Organs of different construction, sepals, petals, and others, are thus 

 laid down at short intervals. 



3. The more the organs of a plant are aggregated at their points 

 of origin the easier it is for malformations to occur, as very small dis- 

 turbances suffice to cause changes in the passage of the organ-forming 

 material into the primordia. A normal construction of so complex an 

 aggregation of organs as the flower can only take place when all move- 

 ments of material and all cell-divisions follow with an almost mathematical 

 accuracy. When, for example, some molecules of such substances as 

 are required for the formation of anthers deviate only the i/iooomm. 

 to the right or to the left from their normal path, or in their passage 

 into the vegetative point of the flower are delayed or hastened, they 

 may enter into, and induce a partial anther-character in, a carpellary 

 leaf or a petal. 



During my investigations into the development of double flowers a 

 I came to the conclusion that Sachs' conception made possible the 

 harmonizing of the facts in the simplest way. In every case we have 



1 Sachs, Gesammelte Abhandlungen iiber Pflanzenphysiologie, ii. p. 1159. 



2 See also Sachs, Uber Wachslumsperioden imd Bildungsreize, in Flora, 1893, p. 217. 



3 Goebel, Beitrage zur Kenntnis gefullter Blutcn, in Pringsh. Jahrb. xvii. p. 207. 



