ULY II, I918] 



NATURE 



365 



or "oceras "; but Geyerina is left as a mystifyiny^ 

 exception, which is just as likely to refer to a 

 brachiopod as to a cephalopod. Seven are modifi- 

 cations of the name of the species chosen as the 

 type ; thus Bifericeras has biferus for its type. The 

 remainder are not so happily devised. Euhoplo- 

 ■fceras has A. acanthodes for its type. Would not 

 Acanthodiceras have conveyed practically the 

 same meanings, and been much more easily 

 assimilated? .4. luridiis is the type for Beaniceras. 

 What is the objection to Luridiceras? 



Among^ the morpholog-ical terms introduced 

 those relating to homeomorphy crystallise our 

 knowledge of this phenomenon and will be valuable 

 for the discussion of other groups of fossils ; . but 

 the series of terms of which " angustumbilicate " 

 is a sample is more cumbersome and confusing 

 than the descriptive phrases it displaces. The use 

 of a formula to express the relative dimensions of 

 the ammonite and its whorls cannot be excelled for 

 conciseness and accuracy,; but the omnibus terms 

 devised to convey the same information have ai; 

 average range of error of 8 per cent., and their 

 use will render ammonite literature still more 

 unintelligible to the average worker. 



Taken as a whole, this work is a most valuable 

 contribution to the science of palaeontology.' ' ' 



Naturforskeren Pehr Forsskal. Af Carl Christen- 

 sen. Pp. 172. (Kobenhavn : H. Hagerup's 

 Forlag^, 1918.) Price 8.00 krone — 95. 



The author of this interesting volume is well 

 known to botanists by his valuable bibliographic 

 work, esf>ecially his work on ferns. We have 

 now to thank him for a welcome sketch of the 

 naturalist of the ill-fated expedition to Arabia in 

 1 76 1 to 1767, which was conducted at the expense 

 of Frederick W of Denmark. 



The volume begins with an account of the 

 expedition and the story of the gradual reduction 

 of the six members to one. Christen Niebuhr being 

 the only survivor. Pehr Forsskal was a Swede, 

 born at Helsingfors in 1732. He was in- 

 scribed as a student at Upsala University, 

 where he attended the lectures of Linnaeus, but 

 showed so strong- a bent towards Oriental lan- 

 guages that in 1753 he migrated to Gottingen, 

 where the celebrated J. D, Michaelis was profes- 

 sor. He was thus equipped both as naturalist and 

 interpreter. 



The results of his labours in this capacity are 

 i well known, as they were published by Niebuhr 

 j on his return to Copenhagen, practically unaltered 

 from the original papers. We have accounts of 

 plants observed in the South of France, Malta, 

 ' Constantinople, Egypt, and Arabia Felix, until 

 ']■ Forsskal's death at Jerim on July 11, 1763, in the 

 ; thirty-second year of his age. 



The text of the present volume is in Danish, but 

 the Appendix of letters from the State Archives 

 \\s more accessible to most readers because thirty- 

 six letters are in German and the remaining four 

 in French. 



NO. 2541, VOL. lOl] 



I LETTERS TO THE EDITOR. 



[The Editor does not hold himself responsible for 



I opinions expressed by his correspondents. Neither 

 can he undertake to return, or to correspond with 

 the writers of, rejected manuscripts intended for 

 this or any other part of Nature. No notice is 



I taken of anonymous communications.] « 



Weeping Forms of Elm. 



A REMARKABLE elm of the variety known as Uhnus 



j serpentina, apparently about sixty years old, is now 



I vigorously growing in a Croydon garden. It has this 



'■ peculiarity, that all its f)ermanent branches are 



curiously contorted and reflexed, while all the shoots 



from one to three years old are pendulous rods, which, 



with the beautiful foliage, form an exterior covering 



reaching to the ground. 



To my knowledge no pruning has been done for 



the last four years by human agency, and it is highly 



I probable that the tree from its beginning as a graft 



j on a stock of Uhnus montana has been allowed always 



to develop itself without human guidance. 

 I Will someone kindly explain how this tree has been 

 I able for many years to maintain its contorted charac- 

 i ter, seeing that all its young shoots, year after year, 

 i are not crooked? 



j I may add that much dead wood of recent growth 

 I falls from the tree every winter, and I have seen that 

 j more of the same kind remains entangled in the con- 

 j volutiojis of the upper branches. 

 I ' W. H. Shrubsole. 



15 Chatsworth Road, Croydon. 



We are informed that there is an interesting re- 

 ference by the late Prof. Meehan, of Philadelphia, to 

 a weeping form of Ulmus americana in Proc. Acad. 

 Nat. Sci. Philad., 1901, p. 356, Like Mr. Shrubsole, 

 j however, Prof. Meehan confines himself to describing 

 I facts; he does not give any explanation of them. — 

 I Ed., Nature. 



"HABITAT GROUPS" IN AMERICAN 

 MUSEUMS. 

 I F)R- B. W. EVERMANN, Director of the 

 Ly Museum of the California Academy of 

 Sciences, gives an account, in the Scientific 

 ; Monthly (New York) for January last, of some of 

 j the "habitat " 6r ecological exhibits of mammals 

 j and birds which have recently been installed in the 

 I museum under his charge, and explains his views 

 with regard to the educational functions of 

 ; museums. With the latter part of h*s subject we 

 are not at the moment concerned ; but as it is pos- 

 ; sible, owing to the kindness of the publishers of 

 the Scientific Monthly, to reproduce here several 

 j of the illustrations which accompany Dr. Ever- 

 I mann's paper, advantage may be taken of this 

 i opportunity to direct attention to some of the 

 beautiful results which have been achieved in the 

 ; United States in exhibiting animals in their 

 natural surroundings. Each illustration has had 

 to have its width cut away by about an inch in 

 order to bring it within the width of a page of 

 Nature, but even with this reduction the mere 

 inspection of the illustrations in question is suffi- 

 cient to induce a feeling of unqualified admiration 

 for these efforts; and, from my own personal ex- 

 pediences in the United States, I am able to go 



