194 SIGNIFICANCE OF MALFORMATIONS IN ORGANOGRAPHY 



by dense tufts of bracts, and this is a natural step towards the phenomena 

 of phyllody brought about by the attack of insects. 



The work of J. Peyritsch l upon the artificial production of double 

 flowers and other malformations is of great interest, and it is unfortunate 

 that owing to the death of the author we have been deprived of the 

 detailed exposition of the results of his experiments which he had pro- 

 mised, and only possess the two short communications cited in the note. 



FIG. ioS. Pteris quadriaurita. ' Witches' broom ' upon a leaf pinna. Its leaves differ in form from tlie normal 

 ones of the fern. The malformation is induced by the attack of the parasitic fungus Taphrina Laurencia. After 

 Giesenhagen. 



In the second of these Peyritsch has shown that in species of Arabis 

 phyllody may be produced by artificially infecting them with aphides 

 provided that the flower-buds are not in too forward a stage of develop- 

 ment. A disturbance of the formation of the sexual organs is associated 

 with the phyllody, the pollen especially being rudimentary and obviously 

 functionless. 



Far-reaching malformations have been produced in Valerianeae and 



1 J. Peyritsch, Uber klinstliche Erzeugung von gefitllttn Bltiten nnd anderen Bildungsabweichnngen, 

 in Sitzungsber. der Wiener Akad. der Wissensch., xcvii (1888) ; Id., Zur Athiologie der Chloranthien 

 einiger Arabis-Arten, in Pringsh. Jahrb. xiii. 



