420 Physiologie. — Palaeontologie. 



which has been killed but appeared normal possessed the conduc- 

 tivity of dead tissue, while tissue which appeared unhealthy often 

 showed a high resistance and therefore a relatively high degree of 

 vitality. G. W. Freiberg (St. Louis). 



Stopes, M. C, Catalogue of the Mesozoic plants in the 

 Department of Geology, British Museum. (The Cretaceous 

 Flora. Part 11. Lower Greensand (Aptian) plants of Britain. 1915.) 



In the present part a total of 44 forms are described, namely: 

 1, Thallophyte; 2. Filicales; 9. Cycadophyta; 27. Conifers; 5. Angio- 

 sperms. The scarcity of ferns and the overwhelming preponderance 

 of Conifers are unusual features in Mesozoic fioras. The species 

 described represent only the sturdier portions of the larger woody 

 Clements of the whole flora then living. As a consequence the 

 absence of herbaceous Angiosperms must not be taken to be of any 

 phylogenetic significance. The Angiosperms described in the present 

 volume are the earliest Dicotyledons recorded for the whole North 

 of Europe, and are the earliest specimens of which the anatomy 

 is known from any part of the world. Many leaf-impressions from 

 deposits somewhat older than the Aptian (e. g. the "Potomac" of 

 America) have been described, but the exact correlation of these 

 deposits with the European beds is still very uncertain. The records 

 of Dicotyledons in beds clearly older than the Aptian (e. g. in the 

 Kootanie and Horsetown beds and also the pre-Aptian Angiosperms 

 and the pro Angiosperms described by Saporta) are not securely 

 established. The Aptian stems described in the present work were 

 Woody plants of a highly advanced and differentiated character, 

 and there is nothing in their anatomy to indicate any more clearly 

 their phylogenetic origin than there is in the stems of the still 

 living genera. The origin of the Angiosperms remains the „abomi- 

 nable mystery" Darwin thought it. The author considers the Solution 

 via the Benettitales an unlikely one especially since highly differen- 

 tiated Angiosperms occur in the strata from which Benettites Gib- 

 sonianus and others were obtained. 



The evidence from the plants points to a relatively cool climate 

 with well-marked seasons. In this connection it is important to note 

 the predominance of Conifers, yet absence of Araucarineae and the 

 occurrence of well-marked growth rings, which are so regulär and 

 normal as to have every appearance of being annual rings. While 

 growth-rings in Angiosperms do not necessarily indicate seasonal 

 change of climate, in the ever-green Gymnosperms they do. 



A concise summary of the previous records of English Lower 

 Greensand plants is given. Practically all the Lower Greensand 

 plants found in the British Isles are from the South east of England. 



Thallophyta. The only Lower Greensand form of any importance 

 is ^^Chondrites Targionü" . 



Filieineae. Weichselia reticulatUj Ward. Described from external 

 impressions. Tempskya erosa, comb. nov. Stems of small diameter, 

 erect, dichotomous and imbedded in a felted mass of their own 

 adventitious roots. Dorsiventral, with the leaves in two rows on 

 one side of the stem, and roots alone on the opposite side. Vascular 

 System of stem a solenostele. Leaf-trace departs as a Single Strand. 

 Roots diarch. 



Bennettiteae. Be^inettites Gihsonianus, Carruthers , is fuUy des- 

 cribed. Bennettites Allchini, sp. nov. Bennettites niaximus, Carruthers. 



