786 TRANSACTIONS OF SECTION K. 



3. On a New Method of Observing Stomala. 

 By Francis Darwin, D.Sc, F.B.S. 



4. Germination Conditions and the Vitality of Seeds. 

 By Miss N. Darwin and Dr. F. F. Blackman, F.R.S. 



5. The Absorption of Water by certain Leguminous Seeds. 

 By A. S. Horne, B.Sc., F.G.S. 



This paper dealt with some of the problems connected with the swelling of 

 cultivated leguminous seeds under different experimental conditions in the light 

 of a knowledge of their anatomy. The trough-like organ figured by Nobbe in 

 ' Handbuch der Samenkunde ' is a secondary development, at least, in the 

 lupine, and, although apparently adapted for the admission of water, did not 

 function in this capacity under the circumstances of the experiments described. 

 The shape of the trough is a distinctive character in certain peas used by 

 Mr. A. D. Darbishire for breeding experiments— c.;/., the bean pea, Express 

 pea, &c. 



In each experiment a number of single seeds was used, and weights and 

 volumes, or both weights and volumes, determined over short intervals of time 

 for continuous periods of twenty-four hours or more, so that the behaviour of each 

 seed could be represented by a curve. The curves obtained for submerged seeds 

 with closed micropyle in some genera — e.g., Vicia Faba — differ considerably from 

 tho curves for unsealed seeds. The use of the micropyle, however, for the 

 admission of water would probably not occur normally in Nature. In every case, 

 directly the seed commenced to absorb, water entered continuously through the 

 seed-coat. Distinctive curve-forms have been obtained for different varieties of 

 the lupine — e.g., white, yellow, and blue — and for Mcndelian peas — e.g., round 

 and wrinkled peas, the bean pea and Express. 



The results obtained by keeping absorbing seeds at different temperatures 

 were complex, the variability depending upon different combinations of variable 

 factors, such as the use of the micropyle, the properties of the seed coat, and 

 the behaviour of the embryo. The data resulting from experiments of this kind 

 may be conveniently represented by means of dot diagrams, wherein each dot 

 corresponds to a definite increase in weight per hour. 



In order to compare the behaviour of certain seed-coat membranes — e.g.. 

 Broad bean, scarlet-runner bean, white Dutch runner bean — and other membranes 

 with respect to osmotically active solutions, numbers of seed-coat osmometers 

 ivere made. Seed-coats of the white Dutch runner bean proved highly satis- 

 factory, the column of liquid rising in the tube against a small initial pressure 

 upon the seed-coat in five days to a higher level than it did in the case of the 

 pig's bladder membrane in seven or eight days under similar conditions. 



These experiments were carried out with the assistance of Miss S. Coull, B.Sc, 

 md Mr. J. W. Holzapfel, B.Sc. 



WEDNESDAY, SEPTEMBER 7. 



The following Papers and Reports were read : — 



I. The Association of certain Endophytic Cyanophycece and Nitrogen- fixing 

 Bacteria. By Professor W. B. Bottomley, M.A. 



Recent investigation of the root-tubercles of Cycas * has demonstrated that 

 the nitrogen-fixing bacteria Pseudomonas and Azotobacter are always found in 

 association with Anabasna in the algal zone of the root-tubercles. Examination of 



1 Proc. Roy. Soc., B., vol. viii., p. 287. 



