June 26, 1896.] 



SCIENCE. 



919 



teen mice were found in the 131 stomachs, 

 and in no case did any stomach contain the 

 remains of more than one. The crow, on 

 the other hand, not onljr prej's upon mice 

 and other small mammals, but even cap- 

 tures young rabbits and eats many snakes, 

 young turtles, salamanders, frogs, toads and 

 fish. The crow also eats many crayfish and 

 other smaller crustaceans which do not ap- 

 pear in the rook's bill of fare. 



In the matter of vegetable food the rook 

 does not seem to indulge in any great 

 variety in April, May and June, but prob- 

 ably the other months would show many 

 additions to the list. The crow eats about 

 every kind of grain that the country pro- 

 duces, besides fruit and acorns or other 

 mast. The crow appears to be far more 

 omniverous than the rook ; in fact, it seems 

 doubtful if there is anything eatable that 

 a crow will not eat, while, as far as shown, 

 the rook seems quite exclusive. 



In the comparison of these two birds the 

 evidence appears to be in favor of the rook, 

 although the economic difference is not 

 great. 



The proportion of harmful insects is some- 

 what greater with the rook, and its vege- 

 table food does not include so many items 

 of useful grains as with the crow. It is not 

 possible, however, to come to any very 

 definite conclusion until more stomachs of 

 the rook shall have been examined, cover- 

 ing the other months of the year. 



F. E. L. Beal. 

 "Washington, D. C. 



AN INVESTIGATION WITH BONTGEN RAYS, 

 ON GEB3IINATING PLANTS. 



The marked attention which the Eont- 

 gen or X-raj's are receiving from investi- 

 gators of this and other countries, and the 

 popular excitement felt in the investigations, 

 render all papers on this subject of partic- 

 ular interest. 



The first record of experiments with 



these rays in their effect on plants known 

 to the writer is a recent article by Alfred 

 Schober presented to the German Botanical 

 Society.* Schober was- led to the investi- 

 gation by the similarity between X-rays 

 and ultra violet light, which was pointed 

 out by E5ntgen in his first paper. The 

 subject appeared particularly worth j^ of in- 

 vestigation, as Sachs had shown that helio- 

 tropic curving is incited in plants by blue, 

 violet and invisible ultra violet rays in 

 about an equal degree with full white light ; 

 while the red, yellow and green parts of 

 the spectrum are apparently inactive. 



Eothert, in his very extensive work on 

 heliotropism, found the cotyledof of ger- 

 minating oat plants to be particularly sen- 

 sitive to the action of light, and these were 

 thus selected for the experiment. Vigorous 

 plants germinated in full light, with coty- 

 ledos from 1 to 2 centimeters long, were 

 selected and set in damp sand in a dark 

 box, the walls of which were about 1 centi- 

 meter thick and blackened on both sides. 

 A Hittorf's tube was placed at one end of 

 this box at the height of the seedlings and 

 about one centimeter distant from the box. 

 The seedlings were arranged at one end of 

 the box so that they were about 2 centi- 

 meters distant from the tube. The inductor 

 had a spark length of about 12 centimeters, 

 and was kept at its highest capacity during 

 the experiment. A photograph of a hand 

 could have been taken under the same con- 

 ditions at a distance of 30 centimeters in 

 five minutes. 



The plants were first exposed to the ac- 

 tion of the rays for 30 minutes, after 

 which an examination showed that no ap- 



* Schober, Alfred, ' Ein Versuoh mit Eoutgenschen 

 Strahlen auf Keimpflanzen. ' Berichte d. Deut. Bot. 

 Gesellsoh. Bd. 14, Heft 3 (April, 1896), p. 108. 



t Cotyledo is a term introduced by Rothert ( Cohns' 

 Beitriige zur Biol, der Pflanzeu, Bd. 7, p. 25) to des- 

 ignate the leaf-like organ of the form of an almost 

 cylindrical closed sheath which appears first after the 

 roots in the germination of grass seeds. 



