46 Mr W. Gardiner, On the Physiological [Nov. 12, 



from botanical terminology? It is certain that neither from 

 their anatomical structure, nor from the appearance presented by 

 their cell-contents, can they be distinctly recognised, and they must 

 be regarded, as Bonnier 1 remarks, solely from their physiological 

 point of view. 



Martinet is inclined to reject a classification based upon their 

 physiological meaning, on account of the fact that one cannot 

 always determine by tasting, that the liquid secreted actually 

 contains sugar ; but as Bonnier points out, a delicate chemical test 

 can always be employed, and it seems best that at present, at any 

 rate, we should accept the suggestion laid down by Schleiden 2 , to 

 renounce all morphological distinction, and simply to regard their 

 physiological function as Bravais 3 so long ago urged. It was a 

 very convenient classification adopted by Caspary 4 to divide 

 nectaries into floral and extra-floral, and in the light of this sugges- 

 tion it seems better that such classification should be adopted 

 rather than that of Mirbel 5 , who separated them into vascular and 

 non- vascular glands. 



Structures capable of secreting nectar are met with on almost 

 every part of the stem, leaf and flower. I cannot here detail 

 the long list which would include all these various instances, but 

 I would draw attention to the fact that they are most fully treated 

 of in Bonnier's 6 very complete paper. To Caspary, Beinke 7 , 

 Poulsen 8 , and Bonnier we owe the greater part of our knowledge 

 with regard to extra-floral nectaries. As to floral nectaries the 

 literature is so enormous and the investigators are so many that 

 I cannot attempt to treat of them in the present paper, but would 

 only draw attention to the papers of the authors I have already 

 cited where complete and abundant references may be found 9 . 



The cells secreting nectar may either consist entirely of 

 epidermal tissue, e.g. the nectary of the stipule of the Bean, or 

 as in the greater number of instances epidermal and fundamental 



1 Bonnier, loc. cit. 



2 Schleiden, Grundz. der wissens. Bot. 1846, Vol. n. p. 244. 



3 Bravais, "Sur les nectaires," Ann. de Sc. Nat. 1842. 



4 Caspary, De Nectariis, Elberfeld, 1848. 



5 Mirbel, Mem. sur Vorganisat. de lajieur. (Mem. de TInstitut, 1808.) 



6 Bonnier, loc. cit. 



7 Eeinke, Jahresbericht Bot. 1875, p. 433. Gottinger Nachrichten, 1873. N. 

 825. 



8 Poulsen, "Om nogle Trikomer og Nectarien." (Videns. Med. K. Jober. 1875.) 



9 At the apex of the sepal of Bomarea Carderi is a structure which is appa- 

 rently a nectary. I have not tested if sugar is present. The vascular bundle 

 bends outward at this point, and lies under a mass of parenchyma, which is not 

 well differentiated from the rest of the tissue, and . is covered by an epidermis 

 richly provided with modified stoma. This was first observed by Lynch. In the 

 fruit of Draecena cristallina a nectary is present at the apex of each of the three 

 ovular leaves. To Lynch is also due this observation. 



