640 NATURAL SCIENCE. 



OCT., 

 iSqc. 



areas " ; but the first does not apply to partial and local changes ; the second, as ^[r. 

 Jukes-Browne has shown, is open to considerable question; and the third, which 

 appears to me of more weight, is an old argument restated, for it depends entirely 

 upon the absence of deep-sea formations in continental rocks. This I have always 

 regarded as the strongest and most important piece of evidence in favour of the 

 permanence of continental areas. I dealt with the subject at some length in the 

 address already quoted, and I can only add that the caution I then recommended 

 in accepting the evidence as complete, and in supposing that no deep-sea deposits 

 e.xist in continental areas where none have hitherto been detected, has been justified 

 by several additional discoveries of such deposits in various parts of the world. 



Professor James Geikie, in the very interesting address recently delivered to the 

 Geographical Section of the British Association at Edinburgh, expressed himself 

 thus: — "The continental plateau and the oceanic hollows have never changed 

 places, although from time to time portions of the latter have been ridged up and 

 added to the margins of the former, while ever and anon marginal portions of the 

 plateau have sunk down to very considerable depths." This appears to me fairly to 

 represent our present knowledge of the subject, and to be in no respect opposed to 

 the views I expressed in 1890. W. T. Blanford. 



The Dispersal of Forest Trees. 



I WOULD ask Naturalists to study during the present month the dispersal of 

 acorns. Seedling oaks are found abundantly in peat-mosses, and on open heaths at 

 considerable distances from any mature trees. The dispersal of the acorns is 

 generally, and I believe correctly, referred to the agency of rooks, which at this 

 season desert the open fields for the oak copses. Actual observations are wanted as 

 to how far a rook will carry an uninjured acorn in its beak, and whether the carrying 

 of the acorn into the open to eat is a habitual action, or only done occasionally. 

 One constaL.iy finds torn (not gnawed) acorn-husks and half-eaten (pecked) acorns 

 in open fields. 



The question involved is a wider one than the mere inquiry : Why do seedling 

 oaks appear in such unexpected places ? Taking the oak as a type of our forest 

 trees, we would inquire : How fast can a forest spread after a climatic or other 

 change has rendered the country habitable ? And also : Can large-fruited trees, 

 like the oak, cross a strait or arm of the sea ? The oak has a large, soft fruit ; if 

 fruit of this character can be carried considerable distances by birds, then it may 

 be possible to account for the whole of our existing flora, without any land-connection 

 with the continent since the passing away of the cold of the Glacial Epoch. 



Clement Reid. 



TO CORRESPONDENTS. 

 All conimimications for the Editor to be addressed to the Editorial 

 Offices, 67-69 Chanceiy Lane, London, W.C, 



Dr. Henry McCook (3100, Chestnut Street, Philadelphia, U.SA.) desires the 

 address of Mr. Stillbers, of London, who is reported to have successfully reared 

 spiders for purposes of silk-culture. His address or references to any published 

 account of his experiments will greatly oblige. 



ERRATA. 

 Owing to the negligence of a clerk, the corrected proofs of Messrs. Jukes-Browne 

 and Cunningham's contributions last month were overlooked. The two last para- 

 graphs in Mr. Jukes-Browne's article on Oceans and Continents were transposed ; 

 and Mr. Cunningham is not responsible for the erroneous statement (in his review 

 of Romanes' " Before and After Darwin," p. 544) that " Haeckel never used the 

 name Prophysema." The Editor regrets the mishap and tenders apologies. 



