42 \Ylsconsin Academy of Sciences, Arts, and Letters. 



Similar facts are also reported by Waldron 82 from North 

 Dakota. AVliile from Porto Kico 83 we learn that the northeast 

 \\in.l prevailing there causes citrus trees to grow slowly and 

 one-sided in unprotected places; the bark looks dead and the 

 nr\v shoots are variously twisted. A case is cited where two 

 similarly planted citrus groves are located across the road from 

 each other but one is protected by a windbreak while the other 

 is fully exposed. The trees had all been set three years and 

 \\viv hearing in the protected grove while in the exposed one 

 they looked as though they "had just been set." Wind-exposed 

 trees were also found heavily infested by scale-insects while the 

 protected ones were practically free from the pest. 



In a very recent paper 84 it is stated that the wind induces 

 dwarfing and the rosette habit, although the structural modifi- 

 cations are attributed to excessive transpiration. 



A like conclusion was recently also drawn by Choux. 85 He 

 found that the stems of Neptunia prostrata and of Ipomea rep- 

 tans grown during the tropical dry season were not only smaller 

 but that their vascular systems were much more strongly devel- 

 oped than in those produced during the wet season. Starch was 

 abundant in the dry season plants and practically absent from 

 those grown in the wet season. 



The hypothesis advanced by Schwendener and subsequently 

 elaborated by Metzger and Schwarz and the more recent one by 

 Jaccard are so simple and imbued with such insidious directness 

 that they are fascinating although not wholly convincing. Af- 

 ter making a brief survey of the observations and experiments 

 by Jost, Lutz, Fabricius, Rubner, etc., it seems as though the 

 occurrence and distribution of radial growth could not be de- 

 pendent on a single factor. It appears for instance that the 

 distribution of elaborated food must in part at least depend upon 

 its place of manufacture and on the channels of its transport, 

 especially when the amount available is somewhat below the 



"Waldron, C. B. Windbreaks and hedges. N. Dk. Agrl. Expt. Sta. 

 Bui. 88. 1910. pp. 11. 



88 Tower, W. V. Insects injurious to citrus fruits and methods for 

 combating them. Porto Rico Agrl. Expt. Sta. Bui. 10:16-20; 35. 1911. 



84 Kroll, G. H. Wind und Pflanzenwelt. Beihefte Bot. Centralbl. 

 30 Abt. 1:122-40. 1913. 



iB Choux, P. De 1'influence de 1'humidite et de la secheresse sur la 

 structure anatomique de deux plantes tropical es. Rev. Gen. Bot. 25: 

 153-72. 1913. 



