DISTINCTIVE CHARACTERS OF HINDI PLANTS. 15 



to <^T()W ill iii)rii:'ht or <)l)ii(iiK' positions and to assuinc the functions 

 of vegetative branches, the flower buds being often aborted." 



LEAF CIIARACTP:RS of HINDI COTTON. 



The leaves of tlie Hindi cotton are characterized by thinner texture 

 and liirhter color, a fresh, bright green that forms quite a definite 

 contrast with the duller grayish or bluish green of the Egyptian 

 leaves. The surfaces of the leaves of the Egyptian cotton are some- 

 what duller and more liaiiy in Egypt than in Arizona, though not 

 so grayish as when the Egyptian cotton is grown in the cool climate 

 of the Pacific coast, near Los Angeles. The color is usually darker 

 before the fruiting stage of the Egyptian cotton is reached, when 

 the foliage usuallv takes on a lighter and more vellowish tone. The 

 dark foliage of the vegetative phase may be retained under condi- 

 tions of abnormal luxuriance, or the change to the yellower shade 

 of green may occur prematureh^ if the plants are affected by some 

 unfavorable condition, such as too much water or too little. 



The veins of the leaves of the Hindi cotton are usually reddish, 

 and the red color becomes very pronounced at the pulvinus or 

 cushion-like thickening at the bases of the veins, wdiere they pass into 

 the petiole or stem of the leaf. The two large veins on each side of 

 the midrib are particularly likely to be grown together at the base, 

 giving the pulvinus of the Hindi cotton an oblong shape. The leaATS 

 of the Egyptian cotton do not have an enlarged pulvinus, the veins 

 passing more directly into the petiole without becoming much swol- 

 len or united at the base. The surface of the pulvinus of the Hindi 

 cotton is naked, or with only a few scattering hairs, while the cor- 

 responding part of the P]gyptian cotton is usually quite hairy. 



The lack of specialization of the bases of the veins in the Egyptian 

 cotton seems to render the leaves less capable of movement. They do 

 not appear to change their positions to face the sun in the morning 

 and afternoon as much as the leaves of the Hindi cotton. The turn- 

 ing of the leaves to the sun renders the Hindi plants more conspicu- 

 ous in the morning and afternoon than in the middle of the day, 

 when the leaves have a horizontal position. Advantage was taken 

 of this fact in making inspections of fields from moving trains, as 

 will be explained later. 



Even in the first leaves or cotyledons of the young seedlings the 

 reddening of the veins and the basal spot enables the Hindi cotton 

 to be recognized and se])arated from the Egyptian. The difference 

 of coloration is not so obvious in the first few leaves that appear 

 after the cotyledons, for even in the Egyptian cotton these are likely 



"Dimorphic P.rnnches in Troiiioal Crop Plants. Bnllotin 108, Bureau of Plant 

 ludustry. I'. S. Dept. of Agriculture, 1910. 

 77267°— Bui. 210—11 2 



