498 [Proc. B.N.F.C, 



the non-botanical observer of being simply leaves, but, as these 

 seeming leaves as they bear flowers, and arise in the 

 axils of leaves and contain green coloring matter, they 

 perform the functions of true leaves, the latter be- 

 coming reduced ; hence the reason for the differentiation. 

 The morphological features of a leaf were next pointed out, 

 these falling into the customary threefold division of blade or 

 lamina, stalk or petiole, and base. Then the difference between 

 a blade or leaf of a grass and one of a laurel, say, was indicated, 

 the former being uniform on both sides, the latter having an 

 upper and an under surface, or, as it is termed, bifacial. The 

 reasons for this difference were alluded to, and also the part 

 played by each characteristic in the life of the plants. The 

 lecturer next dealt v/ith the physiological functions of the leaves 

 in a lucid manner, pointing out the part played in vegetable 

 economy by the green colouring matter called chlorophyll, which 

 substance under the influence of sunlight during the day 

 assimilates the carbon dioxide contained as an impurity in the 

 air, retaining the carbon, which goes to the formation of starch 

 in the leaf, this starch being subsequently converted into sugar, 

 in which form it is conveyed tO' the various parts of the growing 

 plant, there to enter intO' new combinations with other food 

 constituents, and so promote plant development. Other 

 functions of the leaves, such as transpiration and respiration, 

 v/ere next explained, and the whole summed up by the state- 

 ment that the leaves of plants are in reality workshops for pro- 

 ducing the necessary food supplies. Before concluding, the 

 secondary functions of some plant leaves were brought under 

 notice, in which the carnivorous and parasitic habits of the sun- 

 dews and toothwort were taken as examples. Many of the 

 features indicated in the lecture were illustrated by simple 

 laboratory experiments and by dried plants selected from the 

 Club's herbarium. 



The following members joined in the informal discussion 

 which fohov^^ed the lecture: — ^Messrs. R. Welch, M.R.I.A., H. 

 L. Orr, A. Milligan, W. J. Fennell, M.RJ.A., W. J. C. Tomlin- 

 son, and N. H. Foster, the Rev. J. Shells, and the Chairman. 



