47(5 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Soluble Yellow Pigment in the Petals of Papaver .*— lu the 

 yellow cell-sap at the base of tlie petals of Papaver p>jrenaicum, Dr. 

 A. Weiss finds that alcohol causes a ycllow-gi-een precipitate, con- 

 eisting partly of amorphous granules, partly of large curved crystalline 

 needles. Similar structures are also precipitated by solutions of 

 iodine, chloridcj of iron, nitrate of silver, and chloride of platinum. 

 A similar phenomenon is also presented by P. Burzerii. 



Spontaneous Movements of Pigment-bodies, f — Dr- A. Weiss 

 records peculiar spontaucous amoeboid movements which he has 

 observed in the yellow pigment-bodies of the i^eriantli-leaves of Lis 

 Kamorenns, which are separated by narrow colourless intermediate 

 zones. Those pigment-bodies, which lie on the outer walls of the 

 cells, creep about with constant chauLfes of their form and internal 

 structure, putting out protuberances and again retracting them, their 

 substance varying in its homogeneity and in tlie fineness or coarseness 

 of its granulation. Vacuoles arc also constantly making their ai)pear- 

 ance and again disappearing. Similar striking movements and 

 changes of form were observed in the colouring-matters of the flowers 

 of Iris Matthioli and sordida, Tulipa elojans, and Trollius europcaus. 



Excretion of Healing Substances into Wounds. ;}:— Following 

 out the observations of B. Franck,§ Dr. C. Kraus observes that the 

 resinous substances which form the duramen in wood are in general 

 derivatives either of starch or of tannin. He states also that in 

 certain circumstances the healing substances which are poured out 

 on wounded surfaces are derived from the vessels themselves, and 

 sometimes in suflBcient quantities to be observed without the use of the 

 Microscope. 



Firmness of Tissues. || — Prof. S. Schwendener replies to Det- 

 lefsen's objections to his views T[ on the mechanical principle in the 

 anatomical structure of Monocotyledous, bringing forward in support 

 of these views both practical and theoretical considerations. 



Behaviour of the Optical Axes of Elasticity of Cell-walls under 

 Tension.** — Dr. A. Zimmermann has studied the question whether 

 vegetable membranes possess any special elastic properties that are 

 not common to inorganic substances. His general conclusion is that 

 there may possildy be organic membranes which undergo only 

 extremely small changes of their optical properties from pressure 

 and traction ; but that there is no universal contrast in optical 

 properties between organic and inorganic substances. The experi- 

 ments were made on the intcrnodal cells of Nitella fiexilis, the 

 I)eriderm-cells of Betula alba and Prmuis avium, the epidermis of 

 Allium, Cepa, and the cortex of the stem of Foeniculum officinale. 



* SB. K.K. Akad. Wiss. Wien, xc. (1884). See Bot. Centralbl., xxi. (1885) 

 p. 101. 



t SB. K.K. Akad. Wiss. Wien, xc. (1884) (.3 pis.). See ibid. 

 i Ber. Deutsch. Bot. Gesell., ii. (1884) pp. liii.-iv. 

 § See this Journal, ante, p. 88. 



II SB. K. Preuss. Akad. Wiss. Berlin. 1884, pp. 1045-70. 

 i See tliis Journal, iii. (1883) pp. .383, 679. 

 ** Ber. Deu(8ch. Bot. Gesell., ii. (1884) pp. xxxv.-xlvi. 



