NOTES AND MEMORANDA. 307 



blue fluid can be decomposefl, by agitation with benzin, into a yellow 

 and a blue constituent Cyanophyll can also, like crude chlorophyll, 

 be decomposed, both by agitation and by treatment with potash and 

 alcohol, into a yellow and a green constituent. From an alcoholic 

 solution of crude chlorophyll or from cyanophyll there can, however, 

 be obtained, by treatment with potash and ordinary benzin, a pure 

 yellow substance called by Kraus xanthin, in which there is no trace of 

 fluorescence, which is not coloured blue by acids, and which is also recog- 

 nized by presenting three clearly defined absorption-bands in the more 

 highly refrangible, and a weak band (?) in the less refrangible part of 

 the spectrum. If the potash is precipitated from the alkaline-alcoholic 

 solution which is obtained in the production of xanthin, by means of 

 very dilute sulphuric acid, a beautiful green or bluish-green alcoholic 

 solution is obtained, in which tlie green constituent of chlorophyll is 

 contained, termed by Kraus cldorin. This solution, which resembles 

 chlorophyll in its colour, its fluorescence, and in its property of being 

 turned blue by acids, must be considered rather as a mixture than as 

 a product of decomposition. The yellow colouring matter of leaves 

 and of golden yellow petals, which is soluble in alcohol, presents 

 precisely the same spectroscopic phenomena as the yellow ingredient 

 of chlorophyll obtained by shaking with benzin. From the absorp- 

 tion phenomena of the crude alcoholic extract of the petals of Esch- 

 scholtzia californica, it is evident that we have a mixture of two 

 constituents, one reddish yellow and soluble in water and alcohol, the 

 other golden yellow, and soluble in alcohol, but not in water. The 

 residts are the same with the yellow colouring matter of the petals of 

 HemerocaUis fulva and Dumortieri, and the ligulate petals of the mari- 

 gold ; and it seems not improbable that the absorption phenomena of 

 other more or less strongly coloured orange petals and coatings to 

 the fruit, such as those of Berberis Darwinii and Euonymus europcBus, 

 are due to similar causes. 



B, CRYPTOGAMIA. 



Action of Light and Heat on Swarmspores (Zoospores).— In 

 opposition to the observation of many botanists that swarmspores in 

 water group themselves in a determinate way under the influence of 

 light, Sachs has shown by experiment that in emulsions consisting of 

 oil and a mixture of alcohol and water, the fine oil drops also show 

 similar groupings, and that these are caused by currents in the fluid 

 produced by difl:erences of temperature. 



All that had been published on the subject was reconcilable with 



these results, but a statement of Dodel-Port on the behaviour of the 



swarmspores of UlofJirix clashed with this explanation. According to 



him, the spores in the vessels collected on the side next the window, 



which, as the experiment was made in winter, was the colder side, 



while on the other side they flowed towards a lighted petroleum lamp, 



and consequently to the warmest side. Strasburger then took up tlie 



subject, and submitted it to a thorough experimental examination, the 



results of which are published in the ' Jenaische Zeitschrift fiir 



Naturwissenschaften.' * ^ , , .. ,. 



* \ ol. xn. 5a I. 



2 X 



