748 RECORD OF CURRENT RESEARCHES RELATING TO 



Anatomical and Physiological Study of Nectaries.* — Critical 

 Considerations. — Messrs. Darwin, Miiller, Lubbock, &c., consider that 

 the nectariferous tissues accumulate sugar in order to attract insects 

 and effect cross-fertilization. They moreover describe all floral arrange- 

 ments as being contrived to produce this result in a definite manner. 

 M. G. Bonnier concludes, on the contrary, from his numerous observa- 

 tions, carried on since 1871 in the Alps, France, Pyrenees, Sweden 

 and Norway, &c., that the size of the corolla, the development of 

 colour in the floral organs, the perfume, and the spots and striee on 

 the corolla, are not correlated to the formation of nectar, and that 

 they are independent of the frequent visit of insects. 



In dioecious nectariferous plants the insects do not go to the male 

 flowers first, though they are more visible than the female flowers. 



The same flower may be visited in many ways by the same insect. 



The form of the flower may be altered without any sensible modi- 

 cation in the visit of the insects ; they very often gather nectar with- 

 out fertilizing the flowers. The insects that visit the same flower 

 vary according to the quantity of nectar it produces, and those of the 

 same species difier greatly in different countries. 



We cannot conclude from the facts observed that the colour, per- 

 fume, and corolla of flowers are disposed so as to exclude insects not 

 adapted for cross-fertilization. 



In short, there is no ground for admitting a definite reciprocal 

 adaptation between insects and flowers. 



Moreover, nectaries frequently exist without any external nectar. 

 Numerous nectariferous tissues are also found unconnected with 

 flowers. The role of these nectaries is unknown. 



The preceding remarks show that the modern theory on the role of 

 the nectaries is insufficient. 



Anatomical Considerations. — By nectariferous tissue M. Bonnier 

 means all tissue in contact with the exterior, in which the different 

 kinds of sugar accumulate in considerable proportion. 



He examined the sacchariferous tissues by means of cupro-potassic 

 tartrate, polarized light, and fermentation, as well as with absolute 

 alcohol, and microscopically, in more than three hundred genera, and 

 came to the following conclusions. 



There is always an accumulation of saccharine substances, parti- 

 cularly saccharose, near the ovary, and often a localization of it in 

 certain parts of the appendicular organs. 



The structure of the nectaries is very variable. 



Physiological Considerations. — "When the epidermis of the nectari- 

 ferous tissue is furnished with stomata (which is most commonly the 

 case), it is chiefly by these openings that the liquid is emitted ; in 

 other cases it may pass through the non-cuticularized membranes, or 

 by raising the cuticle. 



We may conclude, all conditions being equal, 1st, that the quan- 

 tity of liquid emitted by the nectariferous tissues increases with the 

 quantity of water absorbed by the roots ; 2nd, that it increases with 

 the hygrometric state of the air. By combining the two influences, 



* ' Comptes Kendiis,' Ixxsviii. (1879) p. 662. 



