196 SIGNIFICANCE OF MALFORMATIONS IN ORGAN OCR A PHY 



Turning again to the investigations of Peyritsch l two points seem 

 to me to be of special significance, 



1. In the formation of galls a material in- 

 fluence of the parasite is the cause of the mal- 

 formation. 



2. /;/ the malformations no formation of new 

 organs usually occurs but only a derangement of 

 tJie organs. 



The cases already described of the attack of 

 fungi show us however that in malformations 

 new relationships of configuration may also appear; 

 and with reference to the ' derangement ' of 

 organs I may remark that when a flower exhibits 

 phyllody the foliage-leaves which replace the 

 petals, stamens and carpels, have the ordinary 

 form of the foliage-leaves of the species ; even to 

 the characteristic ' tentacles ' in such plants as 

 species of Drosera. Phyllody is not always com- 

 plete, and then naturally the form of the leaves 

 is more simple, but the extreme cases are always 

 the clearest. Further, when in the doubling of 

 flowers new petals appear these have usually the 

 form of the ordinary petals ; the malformation 

 consists in an abnormal transformation and in a 

 mixing up in some degree of the different organs. 

 But just as in the formation of galls new tissue- 

 elements which are not found otherwise in the 

 plant do not commonly appear, so in these mal- 

 formations nothing new of a morphological char- 

 acter arises ~. What is new is only the com- 



FlG 109. Juncus lampro- 

 carpus. Shoot transformed by 

 the attack of the insect, Livia 

 Juncorum. The vagina of the 

 leaves is greatly developed, the 

 lamina is reduced. 



1 With reference to other form-changes induced by animals see 

 the summary by Frank in his ' Pflanzenkrankheiten, ' Part iii. 



- It is open to question whether this is always the case. It 

 might be otherwise. Herbst, in the ' Biologisches Centralblatt ' 

 for 1895, points to the fact recorded by Solms-Laubach that in 

 the fungus-galls produced upon Polygonum chinense by Ustilago 

 Treubii the tissue of the host-plant furnishes capillitium-like cells 

 which co-operate in the scattering of the spores by increasing, as 

 Solms says, the difficulty of wetting the free-lying cells. Still 

 what really takes place here is that cells of the host-plant are 

 stimulated to elongation by the growth of the fungus and these 

 are, like the tissue of other galls, of use to the parasite, not to 

 the host (see Solms in Ann. Jard. Bot. de Buitenzorg, vi. p. 79^. 

 Moreover there are cell-forms which are non-existent if the develop- 

 ment is undisturbed, for instance, the hair-formations of ' Erineum- 

 galls ' ; and these hair-formations, which are induced by the attack 



