TRANSACTIOXS OF SECTIOX K. ■ 817 



is more liighly developed in some species than in otliers. In L. aevulea, L., and 

 L. iberica, Bieb., the two gyncBcea are completely inclosed, and united with this 

 outer tissue in certain planes. The morphology of this tissue is shown by the 

 intermediate stages to be the result of ths fusion of the bract eolcs of the two 

 flowers. 



The biological signijicancc of the coalescence of the two ovaries of the 

 cyme is probably to be sought in the iruit, where the union is usually more 

 complete and marked than in the flowers, and gives rise in several species to a 

 fahe berrij. This would seem to be an adaptation, in favour of increased seed 

 dispersal, in that the seeds of two flowers, inclosed in what is superficially a single 

 berry, are eaten by birds at one time. 



3. Some Inquirij into tlie Physics of the Flow of Fhnds in Plant Stems, 

 B)j Professor R. J. Andersox, M.D., F.L.S. 



It is evident that the actual area of the canalicular system may vary from 

 place to place, and area is a very important fact to take into consideration. The 

 nature of the fluid is of great importance, for a fluid which is nutrient and natural 

 is o])erated on by the tissues, and whilst its adhesive properties are considerably 

 modified by the vitality of the tissues its physical characters are likely to be 

 changed from end to end of the stem. Osmoses, too, which are ever constant, may 

 change the flow in time. So also may the elasticity of the wood alter, and the 

 resilience, extensibility, pox'osity, and amount of gases contained may all change. 

 The formation of cork very soon alfects the living exposed tissue, and the tissue is 

 rendered impermeable. 



The higher temperatures are more favouraWe to the flow than the lower. In 

 living tissues the ebb and flow associated with chemical interchange is very apt to 

 complicate cases, and what may appear a vital phenomenon may be a physico-vital 

 or a purely physical one. The eflect of 'the organic' in tissues not necessarily 

 living seems to be a very important question. The ' organisation ' leads to phy- 

 sical aberrations which, although not unknown, are rarely met with in so striking 

 a manner in organic substances. One may place in this category the absorption of 

 fluids and rise of temperature in some organic substances, and the restoration to 

 the status quo on drying. Examples of physical movements and phenomena might 

 be multiplied, but they are well enough known. 



Stems of plants were experimented upon by various fluids of various degrees of 

 concentration. The force was secured by a waterhead which acted directly or 

 indirectly on the stems in qnestioji. The principal heights chosen were 9 feet, 

 4 feet, 3 feet 4 inches, and 1 foot 10 inches. The fluids used were water 

 from the house main, distilled water, acidulated water, and water with various sub- 

 stances in solution. The solutions were sometimes very strong and at other times 

 moderately weak. It may be well to note liow far in these cases the results bore 

 out Poisseuille's laws.' 



(1) The greater the force the greater the flow. This seemed to hold generally, 

 but with some odd aberrations not easily explained. 



(:2) The thicker the stem the greater (by far) the amount of fluid passed 

 through. 



(;?) Tlie longer the stem the greater the resistance. 



(4) The higher the temperature the greater the flow, with some modifications 

 and limits. 



The tirst and most striking fact in connection with the experiments was the 

 comparative ease with which almost all the fluids used passed through the stems 

 with some few exceptions. 



(2) The flow at night was generally lower than the preceding day, estimating 

 the hours, and somewhat lower than a few of the midday hours of the succeeding 



' A waterhead of 17 feet and 22 feet as well as higher pressures were tested. 

 1902. 3 G 



