7^ 



NATURE 



[Nov. 29, 1877 



is also interesting. Thus there are 304 endemic species, 

 232 Mascarene species, i.e., plants confined to Bourbon, 

 Mauritius, Madagascai-, and the Comoros ; 66 African 

 but not Asian, 86 Asian but not African ; 145 common to 

 Asia and Africa ; and 225 common to the Old and New 

 World. If we take the percentages we have the following 

 results :— 29 per cent, endemic, 22 per cent. Mascarene, 

 21 per cent, common to the Old and New World, 14 per 

 cent, common to Asia and Africa, 8 per cent. Asian but 

 not African, and 6 per cent. African but not Asian. From 

 this it is evident that one-half of the wild plants of the 

 flora are restricted to the Mascarene Archipelago. 



The orders containing the greatest number of species 

 are the following : — Orchidacece, 79 ; Gramine^e, 69 ; 

 CyperaceiE, 62 ; Rubiaceae, 57 ; Euphorbiaceas, 45 ; 

 CompositJe, 43 ; Leguminosse, 41 ; Myrtacese, 20. There 

 also 168 species of Filices, but it is rather unfair to con- 

 sider the Filices as an order equivalent say to the 

 Euphorbiaceas or Myrtaceee in the above enumeration. 



The descriptive part of the flora is elaborated in the 

 same manner as the colonial floras already published, 

 and is, as already mentioned, almost entirely the work of 

 Mr. Baker, with the exception of the Orchids, Palms, 

 and Pandani. Any one acquainted with Mr. Baker's 

 work will know that any detailed notice of the descriptive 

 part of the present volume is superfluous. 



W. R. McNab 



OUR BOOK SHELF 



Die Geologie. Franz Ritter von Hau^r. (Vienna : A 



Holder, 1877.) 

 It is a good sign both of the progress of geological study 

 in Austria and of the value of this manual by the director 

 of the Austrian Geological Survey, that a second edition 

 of the work has been called for within three years of the 

 date of its publication. A sample of the revised issue 

 which has been sent to us fully bears out the description 

 on its title-page that it is enlarged and improved. The 

 original work, besides its clearly-expressed introductory 

 chapters on general dynamical and mineralogical geology, 

 is especially a valuable repertory of information regarding 

 the structure and palaeontology of the Austro- Hungarian 

 monarchy. In the new edition, Ritter von Hauer is evi- 

 dently doing his best to keep his manual abreast of the 

 time. The book is well-printed, but the author is still in 

 the hands of a very poor wood-engraver. The new cuts 

 are as rude and feeble as ever. _ ^, .., , 



— — — . , '. i £f i ,if j[ a^. .; 



LETTERS TO THE EDITOR 



\The Editor does not Jiold himself responsible for opinions expressed 

 by his correspondents. Neither can he tmdertake to return, 

 or to correspond with the writers of, rejected manuscripts. 

 No notice is taken of anonymous communuations. 



The Editor urgently requests correspondents to keep their letters as 

 short as possible. The pressure on his space is so great that it 

 is impossible otherwise to ensure the appearance even of com- 

 munications containing interesting and novel facts.'} 



Fritz Muller on Flowers and Insects 

 The enclosed letter from that excellent observer, Fritz Miiller, 

 contains some miscellaneous^ observations on certain plants and 

 insects of South Brazil, which are so new and curious that they 

 will probably interest your naturalist readers. With respect to 

 his case of bees getting their abdomens dusted with pollen while 

 gnawing the glands on the calyx of one of the Malpighiacese, 

 and thus effecting the cross-fertilisation of the flowers, I will 

 remark that this case is closely analogous to that of Coronilla 



recorded by Mr. Farrer in your journal some years ago, in which 

 parts of the flowers have been greatly modified, so that bees may 

 act as fertilisers while sucking the secretion on the outside of the 

 calyx. The case is interesting in another way. My son Francis 

 has shown that the food-bodies of the Ball's-horn Acacia, which 

 are consumed by the ants that protect the tree from its enemies 

 (as desciibed by Mr. Belt), consist of modified glands ; and he 

 suggests that aboriginally the ants licked a secretion from the 

 glands, but that at a subsequent period the glands were rendered 

 more nutritious and attractive by the retention of the secretion 

 and other changes, and that they were then devoured by the 

 ants. But ray son could advance no case of glands being thus 

 gnawed or devoured by insects, and here we have an example. 



With respect to Solatium palinacanthum, which bears , two 

 kinds of flowers on the same plant, one with a long style and 

 large stigma, the other with a short style and small stigma, I 

 think more evidence is requisite before this species can be con- 

 sidered as truly heterostyled, for I find that the pollen-grains 

 from the two forms do not differ in diameter. Theoretically it 

 would be a great anomaly if flowers on the same plant were 

 functionally heterostyled, for this structure is evidently adapted 

 to insure the cross-fertilisation of distinct plants. Is it not more 

 probable that the case is merely one of the same plant bearing 

 male flowers through partial abortion, together with the original 

 hermaphrodite flowers ? Fritz Miiller justly expresses surprise 

 at Mr. Leggett's suspicion that the difference in length of the 

 jpistil in the flowers of Pontederia cordata of the United States 

 is due to difference of age ; but since the publication of my 

 book Mr. Leggett has fully admitted, in the Bulletin of the 

 Torrey Botanical Club, that this species is truly heterostyled and 

 trimorphic. The last point on which I wish to remark is the 

 difference between the males and females of certain butterflies 

 in the neuratioa of the wings, and in the presence of tufts of 

 peculiarly-formed scales. An American naturalist has recently 

 advanced this case as one that cannot possibly be accounted for 

 by sexual selection. Consequently, Fritz Miiller's observations 

 which have been published in full in a recent number of Kosmos, 

 are to me highly interesting, and in themselves highly remark- 

 able. Charles Darwin 

 Down, Beckenham, Kent, November 21 



You mention (" Different Forms of Flowers," page 331), the 

 deficiency of glands on the calyx of the cleistogamic flowers ot 

 several Malpighiacese, suggesting, in accordance with Kerner's 

 views, that this deficiency may be accounted for by the cleisto- 

 gamic flowers not requiring any protection from crawling insects. 

 Now I have some doubt whether the glands of the calyx of the 

 Malpighiacese serve at all as a protection. At least, in the one 

 species, the fertilisation of which I have very often witnessed, 

 they do not. This species, Bunchosia gaudichaudiana, is regu. 

 larly visited by several bees belonging to the genera Tetrapedia 

 and Epicharis. These bees sit down on the flowers gnawing the 

 glands on the outside of the calyx, and in doing so the under side 

 of their body is dusted with pollen, by which, afterwards, other 

 flowers are fertilised. 



There are here some species of Solanum (for instance S, palina' 

 canthum) bearing on the same plant long-styled and short-styled 

 flowers. The short-styled have papillce on the stigma and appa- 

 rently normal ovules in the ovary, but notwithstanding they are 

 male in function, for they are exclusively visited by pollen-gather- 

 ing bees (Melipona, Euglossa, Augochlora, Megacilissa, Eophila, 

 n. g., and others), and these would probably never insert their 

 proboscis between the stamens. 



In a few months I hope to be able to send you seeds of our 

 white-flowered violet with subterranean cleistogamic flowers. 

 I was surprised at finding that on the Serra (about i, 100 metres 

 above the sea) this violet produced abundant normal fruits as 

 well 35 subterranean ones, while at the foot of the Serra, though 



