iS93. NOTES AND COMMENTS. 327 



whole of Europe and Asia. He states the following laws : — (i) When 

 a chain of mountains, such as the Alps, the Pyrenees, separates two 

 nations, .... one generally thinks that the crest, the water-shed, 

 divides two races, each inhabiting his respective slope up to the 

 summit. Nothing of the kind, and one can say that the crest of a 

 chain does not separate two races. In support of this statement, 

 Regnault says : — This error is due to the fact that the crest 

 generally serves as a frontier between two States. (2) Ordinarily 

 the race of the country towards which the lesser slope inclines 

 inhabits not only this slope, but crosses the crest and colonises the 

 more rapidly-sloping side down to the plain in which the slope is lost. 

 It is the junction between the rapid slope and the plain where the 

 contact of the two races is to be found. To the second law he adds 

 two postulates: — [a) The mountain chain must be high and long, 

 as the Alps and Pyrenees ; (b) The law is modified by considera- 

 tions of time, geology, climate, &c. Dr. Regnault discusses in some 

 detail the Alps, the Pyrenees, Erz-Gebirge, Caucasus, and the Hima- 

 laya. The lecture, which is highly interesting, will be found 

 printed in Revtie de Geographic, March, 1893. 



Myeloxvlon. 



In the recently-issued number of the Annals of Botany {\o\.\n.,^. 2^), 

 A. C. Seward discusses the affinity of the fossil plant g&nus Myeloxylon. 

 Corda thought it a Palm, Brongniart a doubtful Monocotyledon, while 

 Goeppert referred it to those plants which must be looked upon as 

 prototypes or synthetic types, recognising in its structure the Fern, 

 Gymnosperm and Monocotyledon. Binney, Williamson, Renault, 

 and Kidston make it a fern rachis of the order Marattiaceae, while 

 Schimper, Schenk, and Felix prefer to regard it as the petiole of a 

 Cycad. The present account embodies the result of an examination 

 of some new material from the Millstone Grit, and elsewhere, and 

 also of some specimens now in the British Museurti, and once the 

 property of Robert Brown, The author has had the good fortune to 

 get sections showing very well the structure of the vascular bundles, 

 the form of which closely corresponds with that in Cycads of to-day, 

 while the position of the first-formed wood vessels on the side of the 

 wood next to the bast is also in striking agreement with these. The 

 bordered pits, characteristic of the recent Cycads, were not seen, but 

 there are points of resemblance between the wood elements in both, 

 while the resin canals of recent Cycads and the fossil petioles are 

 practically identical. 



On the whole, the author concludes that the fossil specimens 

 approach more nearly to the Cycads than the Ferns. The few points 

 of difference which distinguish them from the petioles of recent 

 Cycads are, he thinks, far outweighed by the close parallelism in 

 more essential characters, and he looks upon Mydoxylon as an 



