July 9, 1874] 



NA TURE 



193 



Distribution of Physiological Groups in Europe since the 

 Commencement 0/ the Tertiary Period according to our 

 present knowledge of Existing and Fossil Floras 



EXPLANATION OF THE TABLE 

 K.—Mcsntlierr,is. 



A. Existing Megatherms. 



A'. Eeds of Monod, Paudeze (Ileer). Mesotherms are mixed 

 with Megatherms. 



A-. " Gypses d'Aix." Megalherms with Mesotherms C". 



A''. Chiavone and Salcedo (Massalongo). Mesotherms are 

 mixed with Mcgatlierms but the former are in large pro- 

 porlion. 



A''. " Sables superieurs du Soissonnais " (Watelet), containing a 

 large proportion of Megatherms. The stratigraphical 

 position of these beds, it should be noted, is inferred 

 from palce.jntological evidence rather than from super- 

 position. 



A'. Bolca (.Massalongo), although mixed with Mesotherm=, Me- 

 gatherms preponderate. 



A^. Sheppy (Bowerbank, Ad. Bvongniarf, Lyell). 



B. — Existing XeropIiiUs, 

 The countries where fossil floras of this character are to be 



expected have not been worked geologically, and no bed con- 

 taining Xerophiles is known. 



C . — Mesotherms. 

 C. Existing and recent Mesotherms. 

 C. Many floras in the south-east of France worked out by 



Saporta. 

 C^. Meximieux (Saporta). 

 C. S. Jorge, Madeira (Heer). 

 €■* and C". South-east of Frince (Saporta). Some Megatherms 



occur in his lists, but they do not form a fourth part of 



each flora. 

 C. Piedmont (Sismonda). 

 C". (lEningen (Heer). 

 C^ Monod, Paudeze (sec A'). 



C. Dantzig (Heer). The lower bed contains Sequoid, Smilax, 



Myrica, Ficus, Lauraceic, Juglandacex, &c. 

 C". "Gypses d'Aix " (sec A-). 

 C'l. Chiavone and Salcedo (see A^). 

 Q>\ Bolca (see A"). 



0'\ Spitzbergen ( Heer), mixed with Microtherms D'. 

 C"''. Iceland (Heer), mixe:l with Microtherms D'". 



r>. — M:ci otherms. 



D. Existing a;^J recj.it Microtherms. 

 D^. Cannstadt alluvial deposits. 



D'. Laminated lignites of Durnten (Heer). 



Dl Cromer forest bed (Lyell, Heer). 



D''. Spitzbergen (Heer), mixed with C. 



D'". Iceland (Heer), mixed with €'■'. 



E. — Uclcisloiherms. 



E. Existing Hekistotherms. 



E'. Soutlieru Sweden, Denmark (Nathorst). 

 E-. Meckl n'jurg and Cromer below the forest bed (Nathorst). 

 E-'. Glacial clay of Schweizenbach — between Zurich and Con- 

 stance — (Nathorst). 

 £■*. Superficial diluvium of Spitzbergen (Heer). 



.Signs. 



■V When two groups are united by the plus sign it means that 



at least one-fourth of the flora is made up of the second 



group indicated. 

 ? The no:e of interrogation is used to imply that the geological 



age of the bed is doubtful. 



Setting out with the belief that at a most remote period 

 there was all over the globe a high and nearly imiform 

 temperature, followed by a gradual cooling and the deve- 

 lopment of diversities in climates M. de Candolle pro- 

 ceeds to show that the earliest plants must have been 

 Megistotherm. With the exception of the carboniferous, 

 we are too imperfectly acquainted with the floras of Pri- 

 mary and Secondary periods to trace their distribution. 

 At the commencement of the Tertiary period Megatherms 

 occupied all the then land surfaces up to 58". The other 

 groups becam^e gradually separated, and migrated as in- 

 crease of cold drove them from their former areas. The 

 means by which this was effected isamatter of hypothesis, but 

 it is not hypothesis to say that the various groups never 

 sprung from a single group. It cannot be proved that 

 there formerly existed a single form of vegetation, while 

 M. de Candolle urges that tlie surface of the globe cer- 

 tainly had formerly one uniform climate. The distribution 

 of physiological groups indicates two sorts of floras, one 

 tnigratory, the other fi.xed. Intertropical floras have had 

 but few vicissitudes, arctic and antarctic have experienced 

 many. 



We submit this resume of M. de Candolle's proposal 

 and illustration without at present offering any remarks. 



NOTES 



The usual programme of the forthcoming (the 44th) meeting 

 of the Brit Jii Association at Belfast has been issued. The 

 First General Meeting will be held on Wednesday, Aug. 19, at 

 8 a.m. precisely, when Prof. Williamson, F. R.S., will resign 

 the chair, and Prof. Tyndall, F.K.S., President-elect, will assume 



