March 1G, 1906.] 



SCIENCE. 



427 



favorable conditions is necessary to pro- 

 duce the curly top. The most important 

 practical result obtained so far in the 

 study of the disease is the fact that it does 

 not usually attack beets in the same locality 

 or even in the same field two years in suc- 

 cession. 



About twenty lantern slides were used 

 to illustrate the paper. 

 Distribution of Upland Plants near Ann 

 Arhor: Dr. G. P. Burns, University of 

 Michigan. 



The physical features of the country 

 around Ann Arbor are largely the result 

 of giaeiation. The region is made up of 

 morainal ridges between which are nu- 

 merous valleys. In some cases the depres- 

 sion forms a 'pot-hole.' These are filled 

 with swamp or bog flora. 



The soil conditions vary as much as the 

 topography. The glacial deposits are dif- 

 ferent in various parts of the same section. 

 Large contour maps were made and on 

 them the exact locations of the various 

 plant societies plotted. These maps show 

 that our hills are covered with hydrophytic 

 and mesophytic as well as xerophytic 

 plants. 



The factor of greatest importance in de- 

 termining the distribution of upland plants 

 in this region is the position of the im- 

 pervious layer. 



Demonstration of the Geotropic Sensitive- 

 ness of the Elongating Zone of Boots: 

 Professor F. C. Newcombe, University 

 of Michigan. 



The well-known work of Czapek claimed 

 to demonstrate the limitation of the per- 

 ception of gravitation to the apical 1.5 mm. 

 of the root-tip. The present report was 

 divided into two parts, (1) arguing that 

 Czapek had neglected to take account of 

 the inherent tendency of roots to grow 

 straight, and hence had failed to prove the 

 localization of geotropic sensitiveness; and 

 (2) exhibiting a preparation of twelve 



seedlings of Vicia faha that had just been 

 removed from a centrifuge revolving for 

 six hours with a speed about four times the 

 acceleration of gravitation. From each 

 root 3 mm. of the tip had been removed 

 six hours before, and yet all but one of the 

 roots showed distinct outward curves, the 

 bends being within 2 to 4 mm. of the ends 

 of the roots. 



There seems no escape from the conclu- 

 sion that the elongating zone is sensitive to 

 gravitation. 



On the Erroneous Physiology of Elemen- 

 tary Botanical Text-hooks: Professor W. 

 F. Ganong, Smith College. 

 The author pointed out that the recent 

 simplification of methods and appliances 

 of plant physiology accompanying its ex- 

 tension into elementary education, while 

 admirable in some respects, had often 

 resulted in crude, slipshod and illogical 

 apparatus manipulation and reasoning. 

 Various examples of erroneous experi- 

 ments current in the elementary text-books, 

 especially connected with photosynthesis, 

 root-absorption and transpiration, were de- 

 scribed. These errors have arisen partly 

 from a neglect of control experiment, 

 partly from a too-great reverence for the 

 authority of very fallible leaders in sim- 

 plification. The remedy is to be found in 

 the application to elementary experiment- 

 ing of the same logical and control methods 

 we should use for investigation, in concen- 

 tration upon a few important experiments 

 i-ather than in spreading over many of a 

 more showy type, and in the use of more 

 exact and workman-like apparatus which 

 it is often more economical to buy than to 

 make. The paper will soon appear in 

 School Science and Mathematics. 

 The Growth-energy of Trees as Measured 

 hy the Bands of the Common Bagworm: 

 Dr. Hermann von Schrenk, United 

 States Department of Agriculture. 

 The common bagworm (Thyridopterix 



