June 7, 1877] 



NA TURE 



lOI 



fully adapted apparatus must have originated in an organ per- 

 forming some comparatively simple function. The question at 

 issue may perhaps tte s'ated as follows :— In the cases where the 

 nectar-glands are now well developed has there been a special 

 course of structural development in close relation with the need 

 of the plant for protection ? Has there been a course of evolution 

 such as we may believe has taken place in the formation of 

 the food-bodies in Aiacia splurrocphala and Cecrofia pdtata, 

 or should we not rather believe that the sweet secretion has been 

 devefoped in connection with some unknown process of nutrition ; 

 according to this view, a well developed system of glands may 

 continue merely performing some obscure excretory function, 

 and consequently, although the presence of nectar-glands has 

 undoubtedly been of the utmost importance in determining the 

 survival of certain species, yet it is hardly fair to assume that 

 all nectar glands were originally protective in function. For 

 many plants secrete large quantities of sweet fluid, which 

 serves no such purpose. This argument is given by my father in 

 his " Effects of Cross and Self-Fertilisation " (p. 402). In addi- 

 tion to the facts there given in support of this view, a curious 

 case described by Prof. H. HolTmann may be mentioned 

 ("Ueber Honigthau," 1876). He states that numerous lai-ge 

 drops of sweetish fluid appeared on the under-surfaceof the young 

 leaves of a canjellia. He also alludes to a similar abnormal pro- 

 duction of honey-dew on an ivy plant. 



In the case of introduced plants, we see how an already 

 existing quality may, without any special course of development, 

 become of vital importance to its possessor. Thus, Mr. Belt 

 shows ("Naturalist in Nicaragua," p. 74) that the lime, Citrus 

 limonum, is able to exist in a wild state, because its leaves are, 

 from some unknown reason, distasteful to the leaf cutting ants ; 

 whereas the orange, C. aurantium, and the citron, C. medica, 

 can only survive with the help of man. 



Fritz Miiller concludes his letter with some curious facts on 

 kindred sutjects: — 



"Tlie extreme variability of the nectar-glands on the leaves 

 of many plants, is a somewhat remarkable fact. Thus our 

 Citharexylon has normally two large glands at the base of the 

 leaves, but sometimes there is only one, and sometimes none at 

 all ; besides these there are small glands scattered over the 

 surface of the leaf, the number of which varies from twenty to 

 none. Similar variations occur in the nectar-glands of AUhornea 

 eryl/irosfermum, and of a Xanthoxylon. It seems to me pro- 

 bable that in all the cases at present known, these glands serve 

 to attract protecting ants ; and I here agree with Delpino, 

 although I do not hold with him that caterpillars are the chief 

 enemies which are guarded against by Pheidole and Cremato- 

 gaster ; but I think with Belt that these latter ants protect the 

 plant against the leaf-cutting species. Indeed it is precisely 

 those plants which are free from the attacks of ants that seem to 

 be especially well fitted for caterpillars. Thus the larvae of 

 Gynaeria live on Cccropia pdtata, those of Epicalia numilia on 

 Alchorrua crythrospermum. On the Cayien (?) whose leaves are 

 furnished with nectar-glands, and are visited by protecting ants, 

 the caterpillars of many species of Callidryas are found. Finally, 

 as far as I know, all the larva; of the genus Heliconius feed on 

 Passiflora. Moreover, the same relation holds in the case of 

 plants protected in other ways, for instance, by stinging hairs or 

 by poisonous sap. How numerous are the larva; found on the 

 European stirging-nettle. In this country we find the cater- 

 pillars of 'Ageronien' on the stinging Dalechampia ; and 

 again those of some species of Danais on Asclepias, which is 

 protected by its milky juice." Fkancis D.\kwin 



Down, Beckenham, May 21 



Quartzite Implements at Brandon 

 At the recent conference held by the Anthropological So- 

 ciety on the present state of the ■juestion of the antiquity of 

 man, the president, Mr. John Evans, referred to the finding of 

 implements made of quartzite at Brandon, and remarked that as 

 that rock did not exist in the neighbourhood excepting in the 

 glacial drift, the implements must have been made from pebbles 

 obtained from the glacial beds, and were therefore of post-glacial 

 age. This statement was made at the end of the meeting when 

 there was no opportunity of replying to it, and as its eflect must 

 have been great, I shall be obliged if you will allow one who 

 beUeves that none of the palteoliihic implements are of post- 

 glacial manufacture to make some remarks upon it. 



For a full description of the implement-bearing deposits near 



Brandon I must refer to an able paper by Mr. J. W. Flower in 

 the twenty-fifth volume of the Quarterly journal of the Geological 

 Society. Gravel Hill, near Brandon, is an isolated hill risng to 

 a height of 91 feet ahove the river, from which it is nearly a mile 

 di.stant. It is covered with gravel which is mostly, and in some 

 places entirely, composed of quartzite pebbles. Mr. Flower esti- 

 mates that three-fourths of the whole are of quartzite. In this 

 the gravel differs from that of other pits in the neighbourhood of 

 Brandon, as for instance, that at Bromhill, which contains only 

 one thirtieth part of quartzose pebbles. 



At Gravel Hill, along with some hundreds of flint implements, 

 four made of quartzite, similar to that of the pebbles, have been 

 found. All the implenrents are usually found at the bottom of 

 the gravel, and occasionally lie on the chalk. On the supposi- 

 tion that the quartzose pebbles, from which some of the imple- 

 ments have been made, were brought by ice in the glacial period, 

 some such succession of events as the following must have 

 occurred. I. Ice, from the north, carried thousands ot cjuartzite 

 stones and deposited them in immense abundance over a limited 

 area. 2. Man afterwards made implements from some of them. 

 3. The whole of the pebbles were rearranged and formed into 

 beds of gravel with the implements at the bottom, whilst the 

 distinctive character of the deposit was retained. 



This ingenious but complicated theory is not necessary, for 

 quartzose boulders and pebbles are found in deposits much older 

 than the glacial period not very far away froai the locality, and 

 may exist beneath the drit't close to it. It has long been known 

 to geologists that there are many fragments of old crystalline 

 rock in ttie upper greensand. They have been described by Mr. 

 Bonney in his geology of Cambridge, and very fully by Messrs. 

 SollasandJukesBrowne, who state that fiagments of gneiss, mica, 

 and hornblende schists, talcose schists, granites, vein quartz, grits, 

 quartzites, and slates are. very numerous in this bed. It ranges 

 northward from Cambridge, and is lost beneath the surface 

 gravels and boulder clays, but it is not at all improbable that it 

 may run along to the west of Brandon, and there contain even 

 more quartzose fragments than in Cambridgeshire. 



I may remark in conclusion that Mr. Flower, in his descrip- 

 tion, states, that he is disposed with the French geologists, to 

 ascribe the outspread of the gravels to some powerful cataclysmal 

 action, and that he does not know of any boulder clays in the 

 course of the river from which such a mass of pebbles could have 

 been derived. Thomas Belt 



Cornwall House, Ealing 



The Migration of the Swiss Miocene Flora 

 WilH reference to the route the plants took which formed the 

 European miocene flora, I should be glad to know why Dr. 

 Unger considers it to have been Irom America to Europe. He 

 says; "There is more than one reason for thinking that the 

 centre from which our lignite flora has sprung was far away 

 from Europe — in the southern parts of the United States " 

 (Joiirn, of Bot., iii. 17). He thinks that the living flora of that 

 part of America is the lineal descendant of that which gave 

 rise, by aid of " Atlantis," to the Swiss miocene flora. But is 

 enough known of the miocene flora of the United States to infer 

 this? Prof. Hcer says that the methods of comparison he em- 

 ployed " incontestably prove that Switzerland was inhabited by 

 types now scattered over every part of the world [agreeing in 

 that respect with the existing Arctic flora], but of which the ma- 

 jority con espond with species of South U.S. of America; the 

 Mediterranean region ot Europe ranks second ; Asia Minor, the 

 Caucasus, and Japan third ; the Atlantic Isles fourth, and North 

 Holland fifth" (/VVzf. Hist. Ret'., 1862, p. 154, quoted by Oliver). 

 Prof Oliver and Sir Charles Lyell thinii that the route was by 

 Japan, and not by the Atlau'is ; but still (Sir Charles, at least) 

 from America to Europe. Heer, in his " Frimceval World of 

 Switzerland" (vol. i. p. 325, Eng. ed.), says the Glyplostrobus 

 hetcrophylhis of Japan "has probably been derived from the 

 tertiary species" [of Europe]. Similarly, in comparing the 

 Ta.xodiuiii disticlium miocenum with that of America, he ob- 

 serves: "It is very interesting to find that the ancestors of the 

 existing American swamp-cypresses were formerly spread over 

 the whole of Europe, as far as 78" N. lat. Again, of Sequoia 

 Langsdorfii, he observes : "It probably formed a zone round the 

 whole earth in high northern latitudes." 



Instead, then, of regarding either Switzerland or the South 

 U.S. as a "centre," X would suggest that the miocene flora was 

 uniformly spread over the whole of the regions bordering the 



