276 Count Gaston de Saporta on the Temperature 



climate, as is proved by the introduction in our southern dis- 

 tricts of A. excclsa, which, at Hyeres and Nice, bears an annual 

 mean of only 15<=-16° C. ( = 59°-60°-8 F.). 



Hitherto, therefore, most of the genera, with one exception, 

 that we have met with do not seem to have required a com- 

 pletely tropical temperature — that is to say, above a mean of 



20°C. ( = 68°F.)• 

 In advancing towards the Chalk, we shall observe at first 

 nearly the same types at the base of this great formation ; but 

 in proportion as we ascend this curious and still imperfectly 

 known period, the vegetation insensibly acquires a new character. 

 Dicotyledons make their appearance in an incontestable manner; 

 the Cycadese, on the contrary, diminish in number and import- 

 ance; and when, finally, we reach the richer and better investi- 

 gated floras of the Upper Chalk, we observe a combination of 

 the following genera : — 



Ferns: Gleicheniaj Sm. — G. pj-otoffaa, Deh. (Aix-Ia-Chapelle.) 

 Lyff odium, Sw, — L. cretaceum, Deb. (Aix-la- Chapel le.) 

 CyatheiteSj Gopp. — Bonaventurea cardinalis, Deb. (Aix-la- 

 Chapelle.) 

 Conifers : Araucaria, Juss. — Dammarites albens, Gopp. (Chalk 

 of Bohemia.) Araucariaj sp. Deb. in litt. (Aix-la-Cha- 

 pelle.) 

 Sequoia, Endl. — Geinitzia cretacea,VY\g. (Quadersandstein.) 

 Cycadopsis aquigranensis, Gopp. (Aix-la- Chapelle.) 

 Palms : Palmacites, Sternb. — P. varians, Corda. (Quadersand- 

 stein.) 

 Flabellaria, Sternb. — F. chamceropifoUa, Gopp. (Silesia.) 

 PANDANEiE : Pandauus, L. — P. simitdce, Stiehl. (Quadersand- 

 stein.) P. austriacuSy Ett., P. pseudo-inermisj Ett., and 

 P. tfinervis, Ett. (Chalk of Gosau.) 

 Nipadites, Bow. — Carpolithes provincialis, Sap. (Fuveau.) 

 MYRiCEiE : Myrica and Comptonia. — Comptonites antiquus, 

 Nilsson. (Chalk of Scania.) MyricUy sp., Deb. in litt. 

 (Aix-la-Chapelle.) 

 PROTEACEiE : Anadeuia, Leucospermum, Grevillea, Hakea, Dry- 

 andrttj &c. — A very great number of species reproducing 

 the characteristic forms of these various genera and of 

 several others. (Chalk of Aix-la-Chapelle.) 



In this series the Pandanese, and probably the Ferns also, 

 alone betray clearly tropical aptitudes ; the other groups advance 

 at the present day to the north and south far beyond these 

 limits ; but the presence of the Pandanea3 is an important fact, 

 which must be taken into account, as in the present epoch their 

 species (which arc particularly numerous in islands, such as 



