May2o. i9i8 Chemistry and Histology of Glands of Cotton 433 



seeds, and those of the last named were nonglandulate. In C. drum- 

 mondii very inconspicuous glands were present, distributed as in Gossy- 

 pium spp. ; on C. phlomidifolia (a poorly preserved specimen) they were 

 not found on the leaves. The latter specimen only of those examined 

 possessed glands on the petals. C. australis Schum., C. hakeaefolia 

 Hochr., C. argentina Giirke, C. hildehrandtii Garcke, and C. heterophylla 

 Garcke were also examined. In all but the second inconspicuous glands 

 were present in most parts except the petals; usually they were most 

 conspicuous on the involucre. 



Dumont (2) cites the presence of " poches schizogenes" in species of 

 Fugosia and Thespesia as in Gossypmm spp. 



II.— THE NECTARIES 



Four sets of nectaries occur in the cotton plant, one set being floral and 

 three extrafloral. The presence, shape, and number of the extrafloral 

 nectaries vary in different species of Gossypium, and the taxonomic 

 value of these variations has been discussed by Tyler {16). 



The secretory mechanism of each nectary consists of a dense aggrega- 

 tion of pluriseptate glandular hairs, trichomes, or papillae, among which 

 simple nonsecretory hairs may be scattered. The development of the 

 papillae of the floral nectary from modified epidermal cells has been fig- 

 ured and described by Reed {12) ; and in accordance with the generally 

 accepted origin of such structures, a similar development may be inferred 

 for those of the two other sets. At certain periods these papillae secrete 

 a sweet fluid which attracts bees, moths, aphids, ants, and similar insects. 

 Its saccharine nature is evident to the taste, and it yields the reaction 

 characteristic of sugars with Molisch's, Meyer's, Fliickiger's, and Feh- 

 ling's reagents. There is no evidence to show that it is attractive in the 

 least to the boll weevil, though its usefulness in attracting insects which 

 prey upon this pest has been cited by Cook (i). 



The comparatively long and narrow papillae of the floral nectar}- line 

 the inside of the base of the calyx in a band i or 2 mm. wide. In G 

 hirsututn and closely related species the nectary is guarded from the 

 smaller insects by a band of hairs on the calyx above it. One set, usually 

 consisting of three extrafloral nectaries within the bracteoles and alter- 

 nating with them, occurs on the outer base of the calyx. These nectaries 

 are irregularly triangular in shape and not deeply sunken. A set some- 

 what similar but more decidedly sagittate, is found deeply indented in 

 the broadened apex of the peduncle, opposite the centers of the brac- 

 teoles, thus alternating with the intrainvolucral nectaries. Trelease {14), 

 speaking of G hirsutum, states that the nectaries of the outer calyx and 

 peduncle are not present on the first flowers; on subsequent blooms 

 those of the peduncle are formed, and on still later flowers both sets 

 occur. In a variety of G barbadense examined here the inner set ap- 

 peared first, the outer set being absent on early flowers or represented by 

 one nectary only. 



