TRANSACTIONS OF SECTION D. DEPT. ZOOLOGY AND BOTANY. 567 



their being overlooked by other honey collecting insects. For this reason wasps, 

 as Mr. Darwin observes, do not frequent coloured flowers to the same extent that 

 bees do, as they probably meet so often with disappointments in the way of flowers 

 that have been emptied of their nectar previously. Hence it appears that the bee is 

 more highly specialised as a collector of honey than the wasp. 



5. On the Nectar of Flowers. By Alex. S. Wilson, M.A., B.Sc. 



Some observations on this subject made by the author during the past summer 

 revealed several highly interesting points connected with the labours of an insect 

 collecting honey. These are attended with more difficulties than mighty at first 

 sight be supposed, for it appears that nectar is only produced during certain states 

 of the atmosphere — dry warm weather being most favourable. The industry of the 

 bee is probably indispensable to its existence, as a small quantity of honey represents 

 a very large number of flowers visited. In the case of the common red clover, 125 

 heads were found by analysis to give one gramme of sugar. Now, as each head con- 

 tains about sixty florets, even in this plant, which is comparatively rich in nectar, 

 7,500,000 distinct flower-tubes must be sucked for each kilogram of sugar collected. 

 This corresponds to about two and a half millions of visits for a pound of honey. 

 In most of our common flowers the amount of nectar is much smaller, usually 

 dilute and iu many cases absent ; moreover, in some instances it appears to be formed 

 only when the essential organs are mature. If in addition the class of sham 

 nectar producers, which is perhaps larger than has been supposed, and previously 

 emptied flowers, as well as those whose nectaries are inaccessible, he taken into 

 account, it will be seen that a great number of fruitless visits must be made by 

 these insects. Bees, however, do not visit any flower at random, but appear to 

 know which flowers are secreting and which are not, on any particvdar day. Thus, 

 the flowers of Vacnnium Myrtillus were thronged with bees while those of Ule.v 

 Europceus were unvisited, on a day when the former were secreting copiously and the 

 latter were quite dry. The extreme solubility and diffusibility of sugar render it 

 necessaiy that the nectar should be well protected from rain, and various arrange- 

 ments for this purpose are found in flowers — such as the mouth of the flower hang- 

 ing downwards, cushions of hairs, papillse, spurs, &c. In the flower of the prim- 

 rose, if the limb of the corolla be covered with water, it will be found that none 

 can penetrate down the corolla-tube to the nectar, on account of the peculiar 

 character of the surface of the petals causing a capillary repulsion. Were there no 

 such means of protection the sugar would speedily be diffused to parts of the flower 

 where it would be accessible to insects without their being of any service in the 

 way of cross-fertilisation. In the fuchsia, which is rich in nectar, it is to be 

 observed that no nectar is formed before the flower opens, and the amount is 

 greatest at the time when the anthers are ready to dehisce. This in all likelihood 

 happens in other cases where it is more difficult, on account of the smallness of the 

 flowers, to ascertain the conditions. In this flower it is remarkable that three- 

 fourths of the saccharine matter is in the condition of cane or uninverted sugar. 

 Possibly this, taken in connection with the fact that nectaries are not un- 

 frequently aborted or degenerated organs, such as a petal or stamen, may throw 

 some lightjon the question in dispute among physiologists, as to whether nectar 

 should be regarded as a true secretion or simply as an excretion of effete matters 

 from the vegetable cells. It has further a physiological interest, as throwing light 

 on the share which the bee has in elaborating honey, since this substance contains 

 no cane sugar, although on account of the acid reaction of the nectar the process of ■ 

 inversion possibly goes on spontaneously. The extensive character of the operations 

 that would appear, from the foregoing considerations, to be performed by insects 

 which collect honey, enables us to form some conception of the importance of this 

 factor, and will help us to judge of the adequacy or efficiency of this cause, which 

 biologists believe to have exercised in past time an important influence iu modify- 

 ing the size, form, and colour of flowers, as well as in determining the character. of 

 certain organs of the insects by which such flowers are frequented. 



