57 



with the climatic conditions prevailing at this height. This is corroborated 

 by our experiences before the War in the North-Bast of Great Hungary, 

 in the Carpathian Forest district, with a plentiful rainfall. Although large 

 quantities of dodder-infected clover were seeded, the crop of clover seed 

 heirvested was relatively pure. 



Towards the end of the war, considerable quantities of clover seed 

 heavily infected with large-seeded dodder were exported from Hungary to , 

 Bavaria. So far as my experience extends, the large-seeded dodder heis not 

 become assimilated to the soil of Bavaria, no doubt because the districts 

 in which this clover seed was planted lie above the boundary line of the 

 noxious effect of dodder. The conditions in present day Austria are 

 probably similar to those in Switzerland and Bavaria. 



As for the limits of dodder effect within the contracted boundaries of 

 present day Hungary, the whole territory must be regarded as being 

 infected. The whole territorj' lies within the limits of dodder growth, so 

 that this noxious weed may appear in any part of the country, and if it 

 does not actually appear in all parts this is to be attributed to the efficiency 

 of the preventive measures and the methods of extirpation. 



Within this territory there are, indeed, districts, in West Hungary near 

 to the frontier of Styria and Austria, which, in contrast with the 500 mm. 

 rainfall of the Lowlands, have an average annual rainfall of 800 mm., and 

 here also the clover fields are less infected. The region east of these dis- 

 tricts, as far as the Danube, has a rainfall of 700 mm., and still farther east 

 the rainfall decreases to 600 mm. and 500 mm. All these districts lie 

 within the general dodder limit, and also within the limit of the large- 

 seeded dodder. 



Consequently, if I summarise the experiences collected in Hungary, I 

 must say that here the limit of dodder seems to be somewhat below the 

 1,000 mm. rainfall line. 



With regard to the limit of dodder in England, the Journal of the Ministry 

 oj Agriculture, Vol. 30, 1923 : 38-41, contains the important information, 

 that C. Trifolii is not fouiad in Scotland, and its appearance in England 

 north of the Trent up to the boundary of Scotland is of little importance, 

 but becomes more frequent in the more southern and eastern counties. 



Here also, it is impossible not to recognise the connection between the 

 extension of dodder-growth and the condition of the rainfall. The south 

 and east of Englsmd have large areas with a rainfall of 7-800 mm., 

 the more western parts have a rainfall of 8-900-1,000, while north of the 

 Trent there are districts with a still higher annual rainfall. The large- 

 seeded dodder appears to have become nowhere acclimatised to the soil 

 in Great Britain. 



All in all, what I can report to you of the operations of the Committee 

 is biit little, and that, unfortunately, is lacking in precision. Yet I 

 believe that the question can be brought nearer to a solution by the deter- 

 mination of the climatic boxindary-lines, and that even this botuidary 

 line, reported to-day as conjectural, may afford us a handle in estimating 

 the danger of dodder, until we shall have determined a more precise 

 instrument. 



I beg to conclude my report with the following proposals : — • 



(1) The Congress shall renew the appointment of the Dodder 

 Committee ; 



(2) In the first place the Committee shall be recommended to 

 undertake further investigation of the above-mentioned Climatic 

 Lines, the isohyetes, isohypses and , so far as possible, also the isothers ; 



(3) The Committee should also be recommended to approach the 

 question of the limit of dodder havoc from the experimental side. 



It would be of the greatest interest to observe the behaviour of the 

 plant by way of experiment, first in the districts which are believed to be 

 immune and then in the districts which are almost immune. 



