26 



WILD AND CULTIVATED COTTONS 



Unicellu- 

 lar hair. 



Cylin- 

 drical 

 tube. 



Twisted. 



Meta- 

 bolism of 

 cotton 

 cell. 



For methods of examination and study, see Professor H. G. Greenish 

 (' Micro. Exam, of Foods and Drugs/ 1903, pp. 23-6). 



On the Continent of Europe an army of workers were in time 

 also engaged in this inquiry, of whom mention may be made of 

 Sadebeck (' Kulturgewachse der Deutschen Kolonien,' pp. 304-10) ; 

 H. Lecomte (' Le Coton ') ; Vetillart (' Fibres Vegetales,' 1876, pp. 

 130-40) ; Vesque (' Traite Bot.,' 1885, pp. 477-8) ; Semler (' Tropische 

 Agricultur,' in., 1903, pp. 497-502) ; Julius Weisner (' Die Kohstoffe 

 des Pflanzen-Eeiches,' 1903, pp. 239-49), &c. 



MICBOSCOPIO STRUCTURE OF COTTON. Cotton may be defined 

 as a unicellular hair, formed from the cuticle of the seed. If 

 the young ovule (shortly after fertilisation) be cut in section and 

 examined under the microscope, it will be seen that the cuticle (on 

 the immediate circumference of a transverse section) is warted, as 

 it were, through the protuberance of certain superficial cells. If 

 successive sections be made at different stages of growth, it will next 

 be noted that these warts gradually elongate into unicellular hairs, 

 and in time become the floss or wool of the cotton trade. 



If now a mature cotton hair be examined, this will be seen to be 

 not only unicellular, but to consist of a tube or cylinder broadest a 

 little below the middle, gradually tapered toward the apex and more 

 abruptly toward the base that is, the end of attachment. It will 

 further be noted that it is a transparent tube, and if taken from a 

 seed found within a pod that had not opened, it may be discovered 

 to be flattened lengthwise on itself and smooth ; but if from a pod 

 opened naturally, in the process of ripening, the cellular chamber 

 may be observed to have become twisted on its own axis. 



Repeated sections, made at various stages of the seed growth, 

 will reveal the circumstance that, synchronous with the formation 

 of a coating of floss outside, the embryo gradually matures inside 

 the seed. It may thus be inferred that the external appendage of 

 floss is intimately connected with the life of the germ : is intended, 

 in fact, as an additional protection. (Cf. Cook, ' Weevil-resisting 

 Adaptations,' 65-7.) 



Growth neither Constant nor Uniform. If now the growth of the 

 cotton cells themselves be watched, it will be seen that, as they 

 elongate beyond the cuticular level, the nucleus of each, and its 

 patch of protoplasm, gradually gravitate toward one side of the 

 elongation, where they become as it were fixed. Soon thereafter 

 the whole of the inner wall of the elongated cell is coated with 



