320 EEPOET UPON COTTON INSECTS. 



out. These juices are included under the term nectar."* Delpino pro- 

 poses to replace the Linnasan definition of a nectary by the following : 

 " Pars mellifera plantarum angiospermarum propria "; t whence nectar is 

 a honey-like fluid produced by such glands situated anywhere on an 

 angiospermous plant. This not only excludes honey-dew, which Delpino 

 regards as a pathological symptom, but also the nectar which Francis 

 Darwin has found secreted by true glands on Pteris aquilina.; a fern. 

 Darwin} discusses the case of some Orchid flowers which contain a 

 sweet fluid between the walls of their nectaries, whence it is abstracted 

 by insects after they have pierced these walls. This fluid is spoken of 

 by him as nectar. Eeinke defines nectar as " a clear fluid of sweet 

 taste, elaborated by certain aerial parts of plants." 



Though the elimination of a sweet fluid (honey-dew) on the leaves of 

 plants maybe due to a diseased condition of the leaves in many instances, 

 yet as it is of frequent occurrence, and as the nectar in the last case 

 mentioned is not elaborated by specialized glands, it seems best that 

 this should also be included in a definition of nectar. The following defi- 

 nition is, therefore, proposed in the belief that it comprehends all of im- 

 portance that any previous definition has included, and nothing save the 

 honey-dew, just mentioned not included by some good authority. NEC- 

 TAR: a fluid always sapid, usually sweet, often odorous, which is elabo- 

 rated in any part of a plant, remaining where formed or making its v, ay to 

 some other part ; its raison d'etre being the necessity for the removal of 

 some useless or injurious substance, or for some provision to attract nectar- 

 loving animals to the plant for some definite purpose. 



It has long been known that specialized organs for the elaboration of 

 nectar nectar glands exist in the flowers of many plants as well as 

 outside of the floral envelopes of some. These glands, when occurring 

 outside of the flower, always consist of modified epidermal tissue, as 

 shown by Martinet : they may be said to be made up of an inactive 

 supporting portion, the adenophore of Martinet (PI. Ill, Figs. 1, 5, ), and 

 of an active superficial portion, the gland proper (PI. Ill, Figs, l-o, g). 

 These glandular cells are far different from the epidermal cells of which 

 they are but modifications ; thus, in glands from the petiole of the cas- 

 tor-oil plant I found them to be divided by transverse septa ; and in the 

 foliar glands of the cotton plant to be marked by coarse reticulations on 

 their walls, making them appear at first sight as though not simple cells. 

 In the latter case, too, their distal portions are quite separate from each 

 other, so that they resemble, to a certain extent, crowded villi. Within 

 the flower, glands may be of varied structure, sometimes superficial, 

 sometimes deep, possessing less uniformity than elsewhere. 



According to their situation, these glands may be either floral or extra- 

 floral ; the former occurring within the floral envelopes, the latter, without 



*Text Book of Botany, English translation, 1875, p. 500. 



t Ulterior! Osservazione, 1875, p. 85. 



t Fertilization of Orchids, 2cl edition, pp. 36-44. 



$ Pringsheim's Jahrluchtr fur wise. Sot., 1875, x 119, note. 



