542 ORGANOLOGY. 



winter and summer at a temperature of 60 70'. Roots lying on the 

 surface may be frozen, whilst those deeper may go on absorbing sap. An 

 infinity of observations ought yet to be made in this field, and explana- 

 tory hypotheses are altogether inadmissible, as the facts to be explained 

 are not yet known. Meyen, in this instance, falls into the same error of 

 many other naturalists ; they do not like to give up the flattering idea that 

 science, with the exception of a few trifles, is quite complete, whilst in 

 reality we have scarcely obtained an entrance into the wide field it ope n 

 before us. 



B. Development of Light. 



212. Much has been written respecting the production of light 

 from plants. If we separate, however, all fables and delusions 

 from the real truth, but few facts will remain. 



The whitish points of the black, and as yet problematical (?) 

 fungus, Rhizomorpha subterranea, give out, according to A. von 

 Humboldt, a peculiar phosphoric light. Meyen made similar 

 observations on one of the Algae (?), a species of Oscillatoria. 



Decaying fungi, decaying wood, and other parts of plants, give 

 out, it is well-known, light under certain circumstances. 



The matter affording the light in these cases, consisting of a 

 gelatinous matter, may be stripped off; and the light probably owes 

 its origin to a slow process of combustion, at the expense of the 

 atmospheric oxygen. 



The daughter of Linnaeus first observed a lightning-like phospho- 

 rescence in Trop&olum majus during a sultry, tempestuous night. 

 This observation was subsequently confirmed in that and many 

 other, generally yellow and orange-coloured flowers ; every attempt 

 at explanation respecting it is as yet impossible. 



The following constitute the literature on this subject, which I have 

 principally derived from Meyen's Physiol., vol. ii. p. 192, as I could not 

 myself procure many of the works ; and, indeed, I may add, that I could 

 not see any utility in their study without an opportunity of instituting 

 observations : 



Works on the general subject : 



Placidus Heinrich, iiber die Phosphorescenz der Korper. 



Ehrenberg, vom Leuchten des Meeres. 



On the especial subject of light in plants : 



Conrad Gesner, de lunariis. Zurich, 1555. 

 On Rhizomorpha subterranea : 



A. v. Humboldt, iiber unterirdische Gasarten. Braunschw. 1799. 



Nova Acta A. L. C., vol. xi. pt. ii. p. 605. 



On light in decomposing wood and other decomposing parts of 

 plants : 



N. Act. A. L. C., vol. v. p. 482., and vol. xi. part ii. p. 702. 



De Candolle, Flore frang. Paris, 1815, p. 45. 



Link, Elementa Phil. Bot. ed. 1. p. 394. 



L'Institut de 1836, p. 34. 



Scherer's Journal der Chem., vol. iii. p. 12. 



