ETIOLOGY OF MALFORMATIONS 191 



Upon the sucker-shoots of Sambucus nigra 1 the stipules, which are usually 

 arrested, are well-developed and the leaf-lamina is more divided than is 

 usual. Other examples are common. Similarly I have been able by 

 removing the chief shoots to cause the simple primary leaves on the 

 basal lateral shoots of Vicia Faba to grow out into foliage-leaves, or to 

 form intermediate formations between foliage-leaves and primary leaves 

 which any teratologist would recognize as true malformations (see 

 Fig. 94) ; and A. Mann was able in like manner to bring about in a series 

 of investigations, undertaken at my instigation, the partial development 

 into leaves of the tendrils of Pisum sativum. Sachs was able to evoke 

 a very interesting malformation in the roots of Cucurbita by removing 

 all the vegetative points of the shoots : the primordia of the roots lying 

 to right and left in the tissue of the stem beside the stalk of each foliage-leaf 

 grew out into shortly stalked tubers about the size of a hazel-nut or walnut ; 

 on them the root-cap disappeared and the vegetative point was not 

 recognizable, and the axile bundle-strand was broken up into a circle of 

 bundles separated from one another by a tissue containing chlorophyll ; 

 there was thus produced a differentiation of tissue like that of a shoot-axis a . 

 A change, though not so far-reaching in character, is that which arises 

 from less favourable relations of nutrition. Juncus bufonius has the normal 

 trimerous flowers of other species of Juncus. Buchenau 3 found dimerous 

 flowers in dwarfed examples grown upon sterile soil, whilst Juncus 

 capitatus grown under similar conditions exhibited no change in the 

 numerical relationships of its flower. In Juncus bufonius also this varia- 

 tion does not always take place ; when it occurs there is always an 

 evident influence inducing it. With regard too to the distribution of the 

 sexes in normal dioecious plants like the willows, the effect of external 

 conditions sometimes makes itself felt, and pistillate flowers may appear 

 on staminate plants or there may be hermaphrodite flowers, and the 

 converse is the case. Thus Hampe 4 observed in Salix repens that those 

 twigs which sprang from branches growing under water and reached the 

 surface bore female flowers, whilst those which came into flower after 

 the drying up of the water were male. Any disturbance of the normal 

 conditions of vegetation will in general favour expression of the latent 

 possibility that exists to produce female flowers on male plants. Thus 

 Haacke 5 describes the transition from female flowers into male ones in 

 a much mutilated female plant of Salix Caprea. In all these cases we 

 have to deal with definite material influences, and we must also assume 



1 See Fritsch, in Osterr. botan. Zeitsclnift, 1889, Nr. 6. 



- Sachs, Gesammelte Abhandlungen iiber Pflanzenphysiologie, ii. p. 1172. 



3 Buchenau, Kleinere Beitrage zur Naturgeschichte der Juncaceen, in Abhandl. d. naturw. Vereins 

 zu Bremen, ii. 



4 Hampe, in Linnaea, xv. p 377. 5 Haacke, in Biolog. Centralblatt, 1896, p. 817. 



