ZOOLOaY AND BOTANY, MICROSCOPY, ETC. 87 



substance of tMs description imbedded in a brown cell-sap, (EnotJiera 

 biennis, Cerinthe aspera, Calendula officinalis, Tagetes glandulifera, 

 Viola tricolor, SudbecMa laciniata, Digitalis amhigua, and Salpiglossis 

 variabilis. The particles of the pigment are often in a state of active 

 molecular movement ; they are always coloured green by iodine, and 

 are soluble in concentrated sulphuric acid with a deep blue colour. In 

 some other chemical reactions they vary. The pigment appears to be 

 always imbedded in a matrix of protoplasm. 



A solid red pigment was observed in the fruits of Bosa canina, 

 Pyrus aucuparia and Hostii, Convallaria majalis, Bryonia dioica, and in 

 the aril of Euonymus latifolius and europceus, Celastrus candens and 

 Taxus baccata. 



The red pigment in the cortical portion of the root of the carrot is 

 of a very peculiar kind, resembling long pointed crystals. The cells 

 of the scarlet berry of Arum maculatum contain a great quantity of 

 minute brownish-red granules. 



Insoluble violet pigments are rare, but occur in Thunbergia alata 

 and Delphinium bicolor ; while blue granules are found in the fruit of 

 Viburnum Tinus. Brown insoluble pigments were found only in sea- 

 weeds, Fucus vesiculosus and Furcellaria fastigiata. 



The development of the coloured granules does not end with their 

 acting as pigments ; after this period they go through a variety of 

 changes of development or degradation. 



Movement of Sap in Plants in the Tropics* — Observations made 

 in Europe show that the activity of the circulation of the sap has two 

 periods of maximum in the 24 hours, one in the morning, the other, 

 less pronounced, in the afternoon. V. Marcano has carried on a series 

 of experiments to determine whether the same is the case in the 

 tropics. They were made at Caracas in Venezuela, about 10^° N. lat., 

 at a height of 869 metres above the sea-level, where the barometric 

 pressure scarcely varies from 1 to 2 mm., and the thermometer not 

 more than 3° in the 24 hours. The plants observed were Carica 

 Bapaya and a liane. By means of a manometer, two very well marked 

 maxima in the rapidity of the movement of the sap were detected, the 

 first between 8 and 10 • 15 a.m., after which the curve rapidly sinks 

 to zero, remains there for a time, and then rises, between 1 and 3 p.m., 

 to a much smaller height than in the morning, sinking then again 

 gradually to zero, the activity commencing again after sunrise. 



Exudation from Flowers in Relation to Honey-dew. t — T, Meehan 

 refers to the fact that standard literature continues to teach that the 

 sweet varnish-like covering often found over every leaf on large trees, 

 as well as on comparatively small bushes, was the work of insects, 

 notably Aphidee. Dr. Hoffman, of Giessen, who in 1876 published 

 a paper on the subject, is the only scientific man of note who takes 

 ground against this view. He met with a camellia, without blossoms, 

 and wholly free from insects, and yet the leaves were coated with 

 " honey-dew." He found this substance to consist of a sticky colour- 



* Oomptes Kendus, xcvii. (1883) p. 340. 



t Proc, Acad. Nat. Sci. Philad., 1883, p. 190. 



