214 



BOOKS AND CURRENT LITERATURE 



^Ir. Balls disclaims, rather too modestly perhaps, a finished character 

 to his product. Patience for imperfections is asked for — -he pleads that 

 "Egypt has been a lonely place for a botanist." Very well does the 

 reviewer understand the meaning of such a plea, but takes pleasure in 

 saying that Mr. Balls' work, granted to be imperfect and incomplete, 

 needs no apology. Both in the interest of pure science as of economics 

 it is to be hoped that he will continue it. 



The first part of the work deals with the physiological problem to 

 which the author has been impelled by his genetical studies, occupying 

 in their statement the second part. The brief opening chapter is an 

 historical account suggesting a romance worth while reading, were the 

 fragments of evidence now available made the parts of a known whole. 

 At present the earliest date for the existence of the cotton plant in 

 Egypt is B. C. 200 — -a but "trivial" antiquity in Egypt. Following is 

 the account of the physiological studies and of the conclusions drawn 

 therefrom, which will interest especially those, aside from students of 

 cotton, who have studied the phj^siological behavior of plants under 

 semi-arid conditions. 



Seedlings from early sown seed are successfully attacked by the sore- 

 shin fungus at lower temperatures — ^around 20°C. At 33° plantlets are 

 only slightly affected. A critical study of the relation, in the fungus, 

 of growth to temperature leads the author to the view that, at higher 

 temperatures — beginning at about 30°C. — the effect of an additional 

 factor is made manifest — graphically, in the straightening of the growth 

 curve, in the organism by cessation of growth. This "limiting factor," 

 in the sense of F. F. Blackman, is a toxic substance still unidentified, 

 but the presence of which is evident by the resumption (jf growth on 

 its removal from the culture. 



The inhibiting effect of sunshine on the growth of the cotton plant 

 is recorded, and explained as due to the too great loss of water, sufficient 

 to cause eVen a contraction of the stem. The reviewer has found simi- 

 lar conditions to obtain in Alabama at relatively high humidities, as 

 shown by a regular daily reduction in the water content of the leaf, 

 and measurable contraction of the tissues — leaf and stem — during the 

 day. Similar relations have been demonstrated to occur in certain 

 plants at Carmel, California. These, and the data afforded by workers 

 at the Desert Botanical Laboratorj^ indicate that these are facts of 

 probably wide application. Balls further attributes cessation of growth 

 in cotton at higher temperatures (beyond 35°C) to "thermotoxy" — 

 due, as in the above-mentioned fungus to the accumulation of a toxic 



