5i6 



NATURE 



[April 27, 1876 



and the ischium and pubis are both turned backwards, 

 parallel with one another, so as to have almost exactly 

 the same position as in birds. There can be no doubt 

 about this most remarkable point now, as the parts have 

 been found in place in the genus Hypsilophodon. The 

 femur was evidently brought parallel to the long axis of the 

 body, and it has the characteristic ridge between the 

 places of articulation of the tibia and fibula. The tibia 

 has a great crest on its front surface, the fibula is quite 

 small, and the flattened end of the tibia fits on to a pulley- 

 shaped bone exactly like the ankylosed astragalus of a 

 bird. The middle or third toe is the largest, and the 

 outer and inner toes small ; the metatarsals, although 

 separate from one another, have their faces so modelled 

 that they must have been quite incapable of movement. 

 Substitute ankylosis for ligamentous union, and a bird's 

 metatarsus is produced ; in fact the whole structure of the 

 Dinosaurian hind-limb is exactly that of an embryonic 

 bird. 



In the very remarkable genus Compsognathus of the 

 Solenhofen slates, which is nearly allied to the Dino- 

 sauria, and included, with them, in the order Ornitho- 

 scelida, the head is small, the neck extremely long, and 

 the peculiarities of the hind-limb are entirely bird-like ; 

 it also seems that the tibia and astragalus were actually 

 united. The fore-limb, moreover, was very small, and it 

 is certain that Compsognathus must have walked on its 

 hind- legs. 



The question, then, naturally arises, did the gigantic 

 Dinosauria, such as Iguandon and Megalosaurus, have 

 the same mode of progression ? This seems, at first 

 sight, hard to believe, but there is considerable reason for 

 thmking that it may have been the case, for, in the case 

 mentioned above of the great three-toed footprints of the 

 Connecticut valley and others found in the Wealden for- 

 mation, no impression of a fore-foot has ever been found ; 

 so that, even if we suppose that the impressions of the 

 fore-feet were entirely obliterated, as the animal walked, 

 by those of the hind-feet, the former must, at any rate, 

 have been very small. 



When we consider what a very strong piece of evidence 

 this is, we are forced to the cor. elusion that the evolution 

 of birds from reptiles, by some such process as these facts 

 indicate, is by no msans such a wild speculation as it 

 might, from a priori considerations, have been supposed 

 to be. 



{To be continued^ 



THE UNEQUAL DISTRIBUTION OF RARE 

 PLANTS IN THE ALPS^ 



MDE CANDOLLE has recently distributed copies 

 • of a paper communicated by him to the Botanical 

 Congress held at Florence in 1874, in which he explains 

 in a very convincing manner a fact which all botanists 

 have noticed in Switzerland, but the causes of which have 

 not hitherto been properly understood. No one is better 

 acquamted with the plants of the Alps than Mr. Ball, and 

 M. De CandoUe prints as a text to his paper a remark 

 made by the well-known author of the Alpine Guide, that 

 it is matter of curious inquiry to ascertain why the vege- 

 tation of certain districts of the Alps is more varied than 

 that of others. 



Two instances to illustrate this will be sufficient. The 

 mountain chain situated between Italy and the Valais is 

 rich in rare and local plants, while that between the Valais 

 and Canton Bern is veiy poor ; again, after tabulating the 

 species found in Switzerland in single cantons only, while 

 sixty-three are peculiar to the Valais, the Canton Bern 

 has but one. 



The explanations which have been given hitherto have 



' Sur les Causes de I'lnegale Distribution des Plantes rarcs dans la Chaine 

 des Alpes, par Alphonse De_Candolle. (Florence, 1875 



mainly rested on existing physical causes. Wahlenberg, 

 at the beginning of the century, insisted upon the action 

 of soil and climate. Perrier and Songeon have endea- 

 voured to correlate the distribution of plants with that of 

 different geological formations. Griscbach, more recently, 

 cuts the knot by supposing that the Alps have been a 

 centre of vegetation, and that their present distribution is 

 an ultimate fact. 



Ue CandoUe has sought the true reason in the circum- 

 stances which accompanied the retirement of the glaciers 

 at the close of the glacial period. " The valleys and 

 groups of mountains which have at present a maximum 

 of rare species and the most varied flora, belong to dis- 

 tricts in which the glaciers disappeared soonest. On the 

 other hand, where the duration of snows and glaciers has . 

 been most prolonged, the existing flora is poor." ^ 



The objection which may be made that a cause so 

 remote can hardly influence the present distribution, is 

 met by pointing out the extreme slowness with which a 

 vegetation establishes itself, and the persistence with 

 which it maintains its status quo when so established. 

 Thus the rare plants for which the botanists of the six- 

 teenth century were accustomed to visit particular locali- 

 ties may still be gathered there. Again, the Rhone valley is 

 intersected by numerous moraines ; the lower and more 

 ancient are covered with chestnuts, while the higher are 

 more and more barren and still covered only with pines . 



From a variety of causes which De CandoUe enume- 

 rates, it seems probable that the soiUhern and eastern 

 glaciers of the Alps were of smaller extent than the 

 northern, and would consequently be the soonest to re- 

 treat. They also probably furnished a refuge amongst 

 their ramifications on smaller mountains which even in 

 the Glacial period would be without snow in the summer, 

 to some of the ancient Alpine and sub-alpine plants which 

 were driven southwards as the glaciers increased. 



We have therefore the curious fact that some of the 

 most ancient fragments of the Alpine flora are now only 

 to be found on the southern slopes of the Alps. This 

 is the case with species of Primula, Pedicularis, and 

 Oxytropis, which exist neither in the interior of Switzer- 

 land nor in the north of Europe. But it is easy to see 

 that, like the other members of this flora, they were driven 

 south during the Glacial period, returning as the moun- 

 tains reappeared from underneath their snowy covering ; 

 whUe on the northern side they were in great measure 

 exterminated. De CandoUe points out as a fact in further 

 confirmation that the Alpine species of Campanicla, pecu- 

 liar to Mont Cenis and the Simplon and neighbouring 

 valleys, are not related to the Arctic species, but find 

 their nearest allies in Greece, Asia Minor, and the 

 Himalaya. 



The Valais was freed from glaciers while the Mont 

 Blanc district and the interior of Switzerland was 

 still in the condition of Greenland. It was gradually 

 stocked by means of species which arrived from France. 

 The first plants to arrive must have been those 

 which are found at the present time on the Jura 

 and the mountains between Geneva and Chamouni. 

 Established at first in the lower part of the valley, they 

 would ascend as the snow diminished. The remarkable 

 plants of the Grande Chartreuse and of Mounts Vergy 

 and Brezon in Savoy, of the higher parts of the Western 

 Jura, and even of the neighbourhood of Bex in Switzer- 

 land, probably belong to this period. When the perpetual 

 snow and glaciers had disappeared from these mountains, 

 the neighbourhood of the Lake of Geneva, the base of 

 the Jura, and even the commencement of the Valais were 

 more favourably circumstanced. Plants of still more 

 southern origin could then arrive from France. This is 

 probably the date at which the box and many Cistinece 

 and Labiata, characteristic of dry southern districts, esta- 

 blished themselves at the foot of the Jura. Seeds carried 

 from Italy by winds or birds introduced some of the rare 



