Rev. W. A. Leigliton on the Genus Ramallna. 123 



very best quality, and that the solutions be freshly prepared 

 and of the requisite strength. Hydrate of potash is best 

 compounded of equal weights of caustic potash and water*. It 

 is also of importance that the solution used on one day should 

 not be left exposed to the air in a vessel until another day, 

 but thrown away, and the vessel cleanly wiped. Nor should 

 fresh quantities of the solution be added to any reserved from 

 a previous experiment ,* for the proper results will fail. The 

 late severe cold weather has convinced me that temperature 

 has something to do with successful reaction ; for with all 

 properly compounded appliances, I have failed (in various 

 lichens previously experimented upon with satisfactory reac- 

 tions) in obtaining the second red reaction after the yellow 

 one, with hydrate of potash, until I warmed the moistened 

 portion of the lichen at the fire, when the red reaction ensued. 

 Excessive cold would seem therefore to render the second 

 reaction very tardy and insufficient. 



I may also add to the reactions obtained by Dr. Ny lander 

 In the genus Ramcdina another which I have obtained on the 

 cortical layer of the thallus — Avhich, on being moistened with 

 hydi-ate of potash, exhibits no reaction, but on the subsequent 

 application of hypochlorite of lime, shows a feeble yellow 

 reaction, intensified into a deej)er yellow, or even orange, by a 

 second application of hydrate of potash (K — , C faint yellow, 

 K deeper yellow). But this reaction, being observable in 

 all the Ramalince^ does not aid us with any distinguishing 

 character. 



Sixty-five species of Ramallna are described, 33 of which 

 occur in Africa, 27 in North America, 27 in South America, 

 19 in Asia, 18 in Europe, 11 in Australia, 5 in Polynesia; 

 5 are found in the arctic zone, 33 in the north temperate zone, 

 32 in the equinoctial zone, and 14 in the south temperate 

 zone. 



The cortical layer is variously composed : in some species 

 it is homy and subamorphous, or with indistinct cellules ; in 

 others and the generality its external portion is amorphous, 

 and its internal portion is formed of longitudinal tubulose 

 conglutinated filaments. The structure of the cortical layer may 

 be best observed by placing a thin section in hydrate of potash, 

 under the microscope. In the spcrmogonia the sterigmata are 



* The experimenter must also be certain that he obtains from the 

 chemist hydrate of potash ; for it has happened to myself that iodide of 

 potassium was once given me by a respectable chemist, with the remark 

 that " hydrate " was the old name, but " iodide " the modern name for the 

 same chemical. But with it I could not obtain the requisite reactions. 



