HARDWICKE'S SCIENCE-GOSSIP. 



NOTES ON THE COTTON FIBRE. 

 By Walter Henshall. 



I. 



STRICTLY speaking, cotton is not a fibre, though 

 always known as "cotton fibre." It is in 

 reality a vegetable hair, found covering the seeds of 

 the cotton plant when mature, destined by nature to 

 serve the purpose of the dispersion of the seeds, in 

 the same way as the pappus of the dandelion and of 

 the thistle : it has been adapted by man for the 

 greater part of his clothing, and it will be seen how 

 suitable it is for such a purpose. 



The cotton plant belongs to the Nat. Ord. Mal- 

 vaceae, Genus Gossypium, and is cultivated in the 

 tropical zone, and as far as 40 latitude. We have 

 no representative of this genus in England, 

 but in our common mallow we have a fair 

 idea of what the cotton plant is like. The 

 flowers of both are very similar, but in fruit 

 a great difference is noticed. The seeds of 

 the cotton plant, when ripe, are found to be 

 enveloped in a mass of woolly hairs. These 

 hairs or fibres vary in length as to the class 

 of cotton, from three-quarters to about two 

 inches. To give the reader an idea as to the 

 minuteness of these fibres, it has been calcu- 

 lated that there are 140,000,000 individual 

 filaments of American cotton in every pound. 

 The histology of the cotton plant has been 

 strangely neglected by scientific men in the 

 past, and it is only very recently that the 

 subject has been studied. One consequence 

 of this is the wide difference of opinion among 

 botanists, as to the number and classification 

 of the species and varieties of the genus Gos- 

 sypium. Linnaeus divided this genus into five 

 species. Professor Parlatore, a gentleman who 

 thoroughly studied the Botanical relations of 

 "the cotton plant, came to the conclusion that 

 there were seven species. De Candolle reck- 

 oned thirteen species. Other competent botanists, 

 however, consider that there are only four distinct 

 species as below, all besides being merely sub-species 

 or varieties. 



Gossypium Barbadense produces the finest cotton 

 we possess, viz. Sea Island, a long silky cotton. From 

 the variety hirsutum we derive the North American 

 and Egyptian cottons, which form the greatest 

 portion of our supply. It is a shrubby plant, grow- 

 ing to the height of about six feet. 



G. Fcruvianiun, as its name implies, is a native of 

 Peru. It is indigenous to South America, and grows 

 to the height of about ten to fifteen feet. The cotton 

 derived from this species is generally harsh to the 

 feel, like wool, and is known as Peruvian, Brazilian, 

 -&c. 



G. herbaceum is the native cotton of India and 



the East. It is the smallest of the cotton plants, 

 growing to the height of four to six feet. It produces 

 the Surat cottons, which are short in staple. 



G. arboreum is a tree-like shrub, growing to the 

 height of fifteen to twenty feet. It is of little 

 importance from a commercial point of view, as the 

 supply is small. It grows in India and China. 



Cotton fibre, when viewed under the microscope, 

 has a twisted appearance, not unlike a joiner's auger, 

 or a stick of barley-sugar. It is this twist in the 

 fibre that enables us to make thread out of cotton. If 

 cotton were cylindrical like flax, it could not possibly 

 be spun into yarn, as the fibres would be too short, 

 and would not hold together. But as the cotton 

 fibre is twisted, it will be readily seen that in making 

 yarn, the edges of the fibres will fit in each other. I 

 cannot better illustrate this than in the case of rope- 



Fig. 5. — Fibres of American Cotton. X 225. 



making. In making a rope, each strand must be 

 separately twisted, and we know they will then fit 

 into each other. And besides, these edges of the 

 cotton fibre are corded,* and, as when the fibres are 

 twisted together, they lock into each other. This 

 explains why we can make strong yarn out of fibres 

 so short. 



Cotton first appears as a downy covering on the 

 seed shortly after fertilisation. Springing from the 

 cellular tissue below the epidermis, they displace the 

 cells of the epidermis and form a large cell, from 

 which the outward growth of cells commences. Those 

 of my readers who are botanists will understand the 

 usual growth of a vegetable hair, but I must ask 



* These corded edges can be seen with a high power, say 

 i-in. obj. 



