The cotton plant in Egypt, studies in physiology and genetics . uire preciseinformation as to the degree of soil saturation whichproduces these effects under field conditions, but the mainfacts are perfectly clear, and we shall meet with the seriouseconomic effects of this root-asphyxiation at frequentintervals. The stomata.—Certain plant physiologists have AND ENVIRONMENT 39 expressed doubts asto the importanceof the stomata inregidating transpir-ation, 1)111 such iscertainly theirfunction in thecotton plant. Con-sequently, an ex-amination of thestomatal move-ments, so far asthey
The cotton plant in Egypt, studies in physiology and genetics . uire preciseinformation as to the degree of soil saturation whichproduces these effects under field conditions, but the mainfacts are perfectly clear, and we shall meet with the seriouseconomic effects of this root-asphyxiation at frequentintervals. The stomata.—Certain plant physiologists have AND ENVIRONMENT 39 expressed doubts asto the importanceof the stomata inregidating transpir-ation, 1)111 such iscertainly theirfunction in thecotton plant. Con-sequently, an ex-amination of thestomatal move-ments, so far asthey are at presentknown, is necessaryto an understand-ing of the way inwhich the stemloses water. The stomata ofEgyptian cottonplants are foundon both surfaces ofthe cotyledons ; onthe hypocotyl andstem, and on bothsurfaces of the foli-age leaves. A full - grownstoma is about 004mm. in length, andthe mcan fre-quency of theseorgans in eachsquare milli-metre has beenfound to l)e asfollows. 144 the surface Fiu. 38. —Regeneration OF THE Highest lendcached byiiib-soil water Old dead motsthreaded byroots Showing crop of new roots develo weoks from merely one uninjured lateral (thedotted line). Tracing from a blue-print oftlie root itself, iifter Hoating it upon a sheetof glass. Sec Fig. ^o and also ;50. 40 THE COTTON PLANT IN EGYPT chap. Cotyledon : Lower epidermis 275 Upper ,, 200 Hypocotyl and stem 20, itc. Leaf: Lower epidermis 176 to 116 Upper ,, 97 to 44 The total number of these apertures is consequentlyenormous. Such a seedling as that portrayed in Fig. 36,already possesses about half a million. Nevertheless, thecotton plant is not abnormally rich in stomata, thoughthe fact that they are found on both sides of the leafshould be remembered. The functional capability of the immature stomatafound in very young leaves is not clear. The cuticle ofsuch leaves is yet thin, and in all probability it allowssome evaporation to take place. The density of thestom
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