PROCEEDINGS OF THE S0CIP:TV. 115 



Col. H. E. Rawson, C.B., R.E.,F.L.S., who had arranged an exhibit 

 of mounted specimens to ilkistrate some of the points dealt with in 

 Professor Moore's communication, was also unable to be present. His 

 notes, however, were read by Mr. Scourfield, and from them it appeared 

 that the specimens were drawn chiefly from Tropseolum majus, but they 

 were typical of the responses made by several other species to the action 

 of sunlight. The changes of colour and structure were produced by a 

 system of selective screening under an English sun — full sun l)eing 

 screened from the plant at selected intervals of daylight, while paying- 

 due attention to the background. The screens might be at a distance 

 of thirty feet and more. All the colouring-matters of T. majm were 

 affected, and analysis of the observations of the past thirteen years 

 justified the statement that changes of colour and structure were pro- 

 duced at different altitudes of the sun. Low sun of the early morning 

 fostered the yellow colouring-matter, and the highest sun of mid-day 

 the violets, blues, and purples, while middle sun stimulated the reds. 

 Thus by giving a self -crimson form a maximum of low sun the flowers 

 had been changed to yellow, with only fine red honey-guides showing in 

 tlie posterior petals. Such changes reappeared in the plants raised from 

 the seed if similarly screened. In this way a new purple form was 

 obtained from other red and yellow forms which now came true in the 

 open garden. The colour of the foliage also changed, as well as the lo])ing 

 of the leaves. The scent of the flowers varied with the colour. When 

 individual branches of the same plant were differently screened and the 

 .seed allowed to fall and sow itself, two new forms appeared which were 

 well known to gardeners, but had not been previously seen in these 

 experiments, suggesting that " sports " were the response of a plant to 

 peculiar screening of a selective character. While plants were being 

 screened to obtain new colours, changes of structure appeared, which 

 also bedame identified with low, middle, and high sun, and could be 

 repeated at will. Flowers greW' with six, seven, and eight petals instead 

 of the normal five, and their shapes were altered. The spiirs were 

 formed in a way which is stated to be unique, for they extend a petal 

 instead of a sepal, and the number was increased to four. Experience 

 soon enabled such extra spurs to be reproduced at will, together witli 

 the changes in the number and shape of the petals which were cor- 

 related with them. In addition to spur peloria, other " sports " well 

 known to botanists appeared, such as proliferation, fsesciation, leaf- 

 division, synanthy, etc., and were illustrated in the exhibit. They 

 had been produced repeatedly, and a specimen of T. tuberosum had 

 just been deposited in the Natural History Museum, South Kensington, 

 whose leaves were kept entire, or were divided into two, three, four, 

 or five lobes as pre-arranged. The microscope had been used assidu- 

 ously throughout these experiments, the growing flowers being arranged 

 under the objective as the changes were in progress, and some very 

 simple explanations of certain apparently complex phenomena had been 

 obtained. Many of the colour-changes depended upon the form, size, 

 and number of the epidermal papilke, upon the turgidity of the Uving 

 pells, and tlie concentration of their contents, In the leaf-division of 



