57 



entitled "Ueber Gallbildung und Generationswechsel bei Cynips ca- 

 licis und iiber die Circulansgalle". It is, however, a peculiar fact 

 that the construction of this publication is not as good as that of his 

 previous writings. BEIJERINCK apparently has not been able to 

 completely avoid the inclination to let the numerous difficulties 

 encountered during the solution of this problem exert influence on 

 the report when he came to write up his observations. Two para- 

 graphs on the Circulans-gall were inserted between the other para- 

 graphs which all deal with the Calicis-gall and the Cerri-gall. 



In this treatise BEIJERINCK described how he became convinced 

 through circumstantial observations in nature and in his botanical 

 garden, as well as by repeated experiments in the laboratory, that the 

 inhabitants of the "Knopper-galls" which are to be found on the 

 cupule of the acorn of Quercus pedunculata, (the gall-wasp of which 

 received the name of Cynips calicis] is the agamous generation of an 

 insect which has a second generation which is gamo-genetic. This 

 generation has all the characteristics of another genus of the Cynipi- 

 dae, namely the genus Andricus. This second generation supposedly 

 develops in small galls produced by the sting of Cynips calicis in the 

 unripe anthers of the Burgundian Oak (Quercus cerris). The fecunda- 

 ted females of this Andricus species, which BEIJERINCK called A. 

 cerri, were supposed to deposit eggs against the inside of the young 

 cupule of Quercus pedunculata. 



Here the first instance was discovered of a gall-wasp which is 

 heterogenetic as well as heteroecious. 



The occurrence of "Knopper-galls" is therefore, according to BEIJ- 

 ERINCK, dependent on the simultaneous presence of both Oak species 

 mentioned at not too great a distance from each other (these gall- 

 wasps are poor fliers). BEIJERINCK calls attention to the fact that 

 this highly valued tanners' material (the "Knopper-galls" are used 

 in the leather factories and for the preparation of tannic acid) is 

 commonly found only on the cupules of Q. pedunculata in the coun- 

 tries native to Q. cerris, viz., in Austria, Hungary, and south-west 

 Europe, while they are found only sporadically in Germany and the 

 Netherlands. BEIJERINCK'S investigation settled, as far as the Ne- 

 therlands are concerned, that close to the places where this gall was 

 found Q. cerris was indeed present, and that one generation of the gall- 

 insect develops thereon. For other countries this does not seem to have 

 been established. Ross mentions for instance on page 71 of "Die 

 Pflanzengallen Bayerns" 1 ) that the "Knopper-gall" is found in Ba- 

 varia, but that no Q. cerris is present there. No one who, just as the 

 writer, has seen BEIJERINCK'S convincing experiments, can doubt 

 that further investigation will show that where there are "Knopper- 

 galls" there will also be found specimens of the Burgundian Oak. 



') H. Ross, Die Pflanzengallen Bayerns und der angrenzenden Gebiete, Jena 1916. 



