356 



SCIENCE 



[N. S. Vol. XXVI. No. 663 



Survey of Egypt, briefly inquires under the 

 above title (Survey Notes, Cairo, 1906, 18-20), 

 ■whether the deserts bordering- the Nile offer 

 illustrations of " the geogi-aphical cycle in an 

 arid climate" (see J own. Geol., siii., 1905, 

 381^07), and suggests that forms in various 

 stages of arid development are recognizable at 

 many localities. He offers a number of ex- 

 amples of independent basins with local cen- 

 tripetal drainage, which are taken to represent 

 the youthful stage of the arid cycle. " Most 

 members of the Geological Survey [of Egypt] 

 have shown that the Nile valley was once 

 occupied by a series of fresh-water lakes in 

 which calcareous travertine and other lacus- 

 trine products were deposited " ; but the brief 

 text does not suffice to show whether these 

 basins were " initial," that is, due to inequali- 

 ties in the originally uplifted land surface, or 

 whether they were due to the long-continued 

 desert erosion of such a surface, the basins 

 being temporarily occupied by lakes during a 

 moist climatic epoch of brief duration. The 

 probability of the survival to-day of any 

 initial basins in the region of the Nile is 

 contradicted by the evidence of long-continued 

 erosion presented in the preceding note. Ex- 

 amples of the disintegration of drainage, sup- 

 posed to be characteristic of an advanced stage 

 of the arid cycle, are also instanced by Ferrar ; 

 but the disintegration here noted is due to 

 obstruction by invading sand dunes, and not 

 to the excavation of shallow basins by wind 

 action, as suggested in the general scheme of 

 the arid cycle. 



The interest thus manifested in the physio- 

 graphic study of desert forms leads us to hope 

 that their detailed and systematic description 

 may be forthcoming in the publications of the 

 Eg3rptian survey; but the possibility of find- 

 ing, even in the deserts that border the Nile, 

 the results of arid erosion, not dominated by 

 the occasional action of flooded streams, is 

 made improbable by the account of the sud- 

 den rain-floods (" sells ") given by H. G. 

 Lyons, director general of the survey depart- 

 ment of Egypt in his admirable report on 

 " The physiography of the River Nile and its 

 basin " (Cairo, 1906). A few local rain- 



storms occur every winter east of the Nile, 

 where the slope from the desert plateau toward 

 the river is well marked. " In about every 

 second year one or other of the larger wadies 

 comes down in flood, sometimes so suddenly 

 as to carry away camels and sheep. . . . Their 

 effect in eroding the desert is immense. . . . 

 These ' sells ' are less rare than is usually sup- 

 posed, and the dry arid appearance of the 

 desert, together with the rareness of rain, 

 cause the effect of such storms as do occur to 

 be underestimated." Yet on the lower desert 

 upland west of the Nile, it appears that the 

 occasional rainfall " drains into shallow wind- 

 worn depressions and there soaks into the rock 

 or is soon evaporated" (p. 293, 294). 



The reviewer finds difficulty here, as in the 

 preceding note, in the attempt to translate a 

 general descriptive account into a systematic 

 account, in terms of structure, process and 

 stage. W. M. D. 



INTERNATIONAL CONFERENCE ON PLANT 

 3ARDINE88 AND ACCLIMATIZATION 



An important conference will be held under 

 the auspices of the Horticultural Society of 

 New York on October 1, 2 and 3 in rooms of 

 the American Institute and the Museum 

 building of the New York Botanical Garden. 



The preliminary list of papers to be pre- 

 sented is as follows : 



D. T. MacDougal, Tucson, Ariz.: "The De- 

 termining Factors in the Seasonable Activity of 

 Plants." 



Henry C. Cowles, University of Chicago: 

 " Factors that control Acclimatization." 



B. L. Livingston", Tucson, Ariz. : " Evaporation 

 as a Climatic Factor influencing Vegetation." 



Eenst a. Besset, Subtropical Laboratory, Mi- 

 ami, Fla. : " Air Drainage as affecting Hardiness 

 of Plants." 



Fkederic E. Clements, University of Nebraska : 

 " The Real Factors in Acclimatization." 



W. M. Hays, Assistant Secretary of Agricul- 

 ture: "Plant Improvements needed in Specific 

 Cases." 



J. C. Whitten, Missouri : " Comparative Hardi- 

 ness of Plants of the same Variety from Northern 

 and Southern Points." 



M. Robert, Algeria : " Observations on Eu- 

 calyptus Hybrids; The Japanese Loquat in Al- 



