2C4 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



the absorption of light by the pigment-spot; in the large majority of 

 animal eyes the presence of a layer of pigment in connexion with the 

 actual percipient organs seems to be necessary; light exerts a very 

 dehnite stimuhis upon the chlorophyll bodies of some Algae and foliage 

 leaves, resulting in their movement into positions in which they can 

 be more effectively illuminated (why should not a similar stimulus bring 

 about the orientation of the leaf itself if the chlorophyll grains are capable 

 of movement?); the rays absorbed by the chlorophyll, which are func- 

 tional in heliotropism, are the chemically active rays; chemical changes 

 taking place in the chlorophyll would afford a more satisfactory explana- 

 tion of the origin of the stimulus than the pressure of light upon the 

 cyijoplasm. 



With the exception possibly of the few special cases in which the 

 light is concentrated upon the chlorophyll grains, there is no satisfac- 

 tory evidence to show that the lens-shaped cells or local cuticular 

 thickenings can be regarded as special adaptations, either for light 

 perception or for the more efficient illumination of the chlorophyll grains, 

 although it is possible they may be of use for both purposes. — A. D. C. 



Peridermium Strobi, the Blister of Weymouth Pine. By 



Dr. W. Somerville (Quart. Jour, of Forestry, vol. iii. 3, p. 232). — The 

 author considers that, owing to the prevalence of this disease, the 

 Weymouth pine in this country is almost doomed. Pinus Cembra is 

 rarely seriously affected, but other young five-leaved pines, particularly 

 P. Strohus and P. monticola, are destroyed wholesale. P. Lamhertiana 

 and P. excelsa are also attacked. The spores of the form of the fungus 

 which attacks the pine, known as Peridermium Strohi, are produced in 

 enormous numbers and in great masses on the bark in April and May, 

 and these spores attack species of Eibes, producing fructifications on 

 the leaves of these plants in July. This form (the teleutospore stage) 

 is known as Cronartium ribicola. The author considers that the only 

 thing to do in this country is to stop the cultivation of five-leaved 

 pines, and counsels the authorities of Canada and U.S.A. to prohibit 

 the importation of five-leaved pines and species of Bibes, so as to 

 prevent the spread of the disease to America, where it is at present 

 unknown. — F. J. C. 



Pharmaceutical Institute of the Berlin University. (Not. 

 Konig. Bat. Berlin, No. 45, vol. v. pp. 115-121). — (A) Caoutchouc 

 from East Africa. Samples of sap were examined : Landolphia Kirkii 

 contained 78'14 per cent, pure caoutchouc, L. florida 15'33 per cent. ; 

 but better results would probably be obtained by improved methods of 

 tapping and treatment. L. parvifolia contained 75'2 per cent, resin 

 and 13'6 per cenu. caoutchouc, and is of little commercial value. 



(B) Sap of Euphorbia Tirucalli contains little rubber, but may prove 

 a useful substitute for mastic. 



(C) Oil from the seed of Mimusops javensis (?). This fat melts at 

 40^ C, and yields, on saponification, 96'66 per cent, fatty acids and 



