SECTIONAL TRANSACTIONS.— K. 409 



that parasitic fungi penetrate plant cuticle by purely mechanical means. By the 

 use of a series of membranes of graded resistance the mechanical penetrating power 

 of various fungi can be roughly compared. 



Intact plant-surfaces which are not attacked by a given fungus are readily 

 penetrated when the support of the underlying tissue is removed — -e.g. when the tissue 

 is killed by antiseptics or other agents, or when the supporting tissue is cut out. For 

 this purpose it is not necessary, however, to kill the supporting tissue. Temporary 

 reduction of turgor by plasmolysis is equally effective. 



1 7. Discussion on Vegetative Propagation. 



(a) Prof. J. H. Priestley. 



For the perpetuation of many strains of cultivated flowering plants which are 

 the product of long periods of selection and hj'bridisation, no method is available save 

 that of vegetative propagation, and no practice is more commonly employed in 

 horticulture. At the same time success or failure in vegetative propagation is a matter 

 •of experience, and generalisations as to the conditions for successful propagation are 

 •founded upon empiricism. A study of the process of vegetative propagation in the 

 light of the development and anatomy of the flowering plant suggests that importance 

 attaches to the following considerations :- 



1. Roots and shoots differ in their mode of growth and in their nutrition under 

 conditions of vegetative propagation ; they originate in different tissues and their 

 production is differently affected bj' external conditions. 



2. The production of new roots and slioots in a Monocotyledon- is a very different 

 problem from that presented by the JJicotyledon. In the latter the new growing 

 points arise in close association with the two cylinders of secondary meristematic 

 tissues, the vascular cambium and the cork phellogen. 



It is suggested that no interpretation of vegetative propagation will prove 

 practicable until a much wider knowledge is obtained of the processes governing the 

 origin of meristematic tissue and its maintenance in healthy activity. From this 

 standpoint the conditions governing the activity of the two cambial cylinders of the 

 Dicotyledon are briefly examined. 



(6) Prof. Neilson Jones. 



(c) Dr. R. C. Knight. 



(d) Dr. R. J. D. Graham. 



(e) General Discussion. 



18. Dr. Macgregor Skene and Miss G. L. Stuart.— T^e Physiology of 



Sphagnum. 

 The cause of the sensitiveness of Sphagnum to alkaline solutions has been investi- 

 gated by a new method. By using carbonate-bicarbonate buffer solutions it is possible 

 to vary the hydrogen-ion concentration and the concentration of salts independently, 

 and to show that low values of the former and high values of the latter cause injury. 

 Marked antagonism between different bases exists under certain conditions. No 

 «vidence was obtained of the dependence of healthy growth on a particular basic ratio. 



19. Dr. B. Millard Griffiths. — The British Freshwater Phy to plankton. 

 The free-floating microflora (phytoplankton) of ninety-four English lowland waters 



has been examined. The phytoplankton considered as one of the communities of 

 aquatic-plant association. Its habitat conditioned by initial water-supply, size of 

 basin, local topography. The salts-abundance habitat ; its micro-, mero-, and 

 holophotic variations and associated plankton types ; relation to corresponding 

 salts-deficiency habitat. General habitat ranges of common species. Relation of 

 British F.W. phytoplankton to that of other regions. 



20. Mr. C. Leonard Huskins. — Cytological and Genetical Studies of the 



Origin of Fatuoid Oats. 

 A comparative cytological study of the miorosporogenesis in fatuoids from 

 various varieties of cultivated oats and in pure species of Avena has shown certain 



