384 SECTIONAL TRANSACTIONS— J, K. 



say. They may be of the environment, although it hardly seems likely from the 

 available evidence. Or they may be subjective, such things as degree of interest, 

 practice, fatigue, &c. 



The arithmetical durations are so constant that one at once suspects them to be 

 due to something in the environment. Again, however, there is a doubt. Control 

 experiments show that they are just as strong, even when special precautions have 

 been taken. Further research on this point is required. 



There are then many puzzUng features in the research. On the whole, however, 

 it would appear that the work curve, as commonly produced, is far more definitely 

 rhythmical than is usually supposed. 



SECTION K.-BOTAIMY. 



(For reference to the publication elsewhere of communications entered in the 

 following list of transactions, see p. 430.) 



CAPE TOWN. 

 Tuesday, July 23. 



Prof. R. S. Adamson.— TAe Vegetation of the Cape Peninsula. 



Mr. R. D'O. Good. — The Geography of the Genus Coriaria. 



Coriaria is the only genus in the Coriariacece, a famUy of polypetalous 

 Dicotyledons of very uncertain affinity. 



The genus is, geographically, almost unique, since it is found in no less than four 

 widely separated parts of the world, i.e. Western Mediterranea ; continental and 

 insular Eastern Asia, New Zealand, New Guinea and parts of Polynesia ; Western 

 South America and Central America. 



It can be divided into three quite distinct subgenera of which two (one monotypic) 

 are confined to the two northern generic areas, and one is confined to the southern 

 areas. 



A number of fossils have been ascribed to Coriaria, but nearly aU are merely 

 detached leaves which may or may not belong to the genus. Of particular interest 

 is a complete fossil branch with leaves and fruits from the Oligocene of Southern 

 France, indistinguishable from a species now living in the Himalayas. 



The present discontinuity within the northern and southern hemispheres can be 

 attributed largely to the immediate or subsequent effects of the climatic changes 

 culminating in the Pleistocene Glaciation. The discontinuity between the two hemi- 

 spheres presents a difficult problem, involving the question of the point of origin of 

 the genus and the directions in which extension of area has taken place especially 

 across the tropics. Several theories can be made to explain the facts, but it is sug- 

 gested that a modified theory of continental movement involves as little hypothesis 

 as any other. 



Mr. W. N. Edwards. — Paradoxopteris, an African Fossil Fern Stem. 



The genus Paradoxopteris was instituted by Hirmer for a curious petrified stem 

 from the Cretaceous of Egypt, which he had previously referred to Osmundites (?) ; 

 it was stiU included in the Osmundacese and was described as consisting of a mass 

 of leaf-traces, the stem stele being unknown. 



A different interpretation is now proposed, and the vascular system is regarded 

 as being a highly complex example of polycj^cly, the supposed Osmunda-\ike leaf- 

 traces being stem meristeles, more or less concentrically or spirally arranged. 



The nearest approach to this structure among recent ferns is to be found in 

 Angiopteris, and it is possible that the relationships of Paradoxopteris may be with 

 the Marattiaceae. The genus is now also recorded from the Cretaceous of Darfur, 

 on the evidence of specimens recently collected by Mr. G. V. Colchester, and the 

 possibility of its connexion with the wide-spread Lower Cretaceous frond-genus 

 Weichselia is discussed. 



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