SCIENCE-GOSSIP. 



33 



DEAD FLIES ON GRASS. 



M 



V father, whilst walking in Mereworth Woods, 

 the Autumn of 



Kent, 



near Maidstone 

 1889, found the 

 grass by the side 

 of the footpath 

 decorated with 

 dead flies, in the 

 manner shown 

 in the specimen 

 now forwarded to 

 you. Although 

 many other spe- 

 cies of flies were 



[We have figured the grass, and the flies, which 

 are specimens of the dipterous insect, Melanostoma 

 scalar e, Fab. Mr. (!. H. Verrall, to whom we 

 have submitted them for his opinion, considers it 



abundant in the woods at the time, there appeared 

 to be only one kind among the dead flies on the 



grass. The in- 

 fected sprays of 

 grass were quite 

 common for 

 about half a mile. 

 Can you tell me 

 anything about 

 this incident ? 



H. S. Fkemi.in. 

 Mereworth, Kent ; 

 Feb. 1894. 



probable that the flies died from the attacks of a 

 parasitic fungus (Empusa muscu) which is so fatal 

 to common house-flies in the autumn of some 

 years. — Ed.] 



PLANT COLOURATION. 



"PHE subject of flower colouration has recently 

 been discussed in these pages with very varied 

 conclusions, but I have been surprised to find that, 

 save by Mr. Robertson (vide vol. xxix, pp. 131 etseq.), 

 little or no notice has been taken of the colours of 

 other parts of plants, which ought surely to throw 

 some light on those of flowers. The following facts 

 I have thrown into several groups, and do not pre- 

 tend to have classified according to their (unknown) 

 causes and laws. They tend to show that a close 

 correlation, or connection, exists between the 

 colours of different parts of plants, whether flowers, 

 fruit, stems or roots. 



Firstly. I have noticed that plants have a 

 tendency to reproduce in the bracts and stems the 

 colour of the flower or fruit. The lily of the valley 

 (Convallavia majalis) has white bracts, the wild 

 hyacinth (Hyacinthus non-scriptus) has blue. Fuch- 

 sias with red sepals have often reddish peduncles. 

 The dodder (Cuscuta cpithymum) and the London 

 pride (Saxifraga umbrosa) alike have their calyx and 

 stem of the same reddish colour. In some plants 

 where this is not obvious to the naked eye, a 

 transverse section of the stem beneath the micro- 

 scope will reveal that the cells of the corky envelope 

 between the epidermis and the chlorophyl-bearing 

 cells contain traces of a pigment the same as the 

 flower or fruit ; thus, those of the lilac (Syringa 

 vulgaris) are frequently of a lilac hue ; those of the ivy 

 (Hedera helix) are occasionally pink, a diluted form of 

 the colour of the berries, I believe ; the young stems 

 of the peach (Persica vulgaris), on the side exposed 

 to the sun, colours a bright pink, which is also due 

 to a pigment which is dissolved in the cell-sap of the 

 corky envelope. The colour in these cases can hardly 

 be due directly to insect preference, though, possibl \ , 

 to an overflow of colouring-matter from the flower. 



Secondly. That despite their totally different 

 environments, the coloured roots of beet and carrots 

 are coloured in the same way as flowers ; by 

 chromoplasts in the case of the carrot, and a 

 dissolved pigment in the beet. I do not know 

 whether green or blue roots exist ; light is generally 

 necessary for the development of green, but some 

 recent observations tend to show that it is not 

 necessary for submerged leaves. That sunlight 

 may be necessary for the development of other 

 colours I have shown (Science-Gossip, vol. xxviii. 

 p. 45) in the case of the flower of Geum cocciheum, 

 and just now in the case of the peach stem, and I 

 suppose no one would deny that it is necessary for 

 the colouring of fruits. 



Thirdly. That in the case of cultivated plants, 

 if a species has different-coloured varieties, the 

 green of the foliage varies with the colour of the 

 flower, i.e., is dark or light as the flower is white 

 and pink, or dark red and blue. A florist, long 

 before they are in bud, can pick out dark-flowered 

 plants of sweet William (Dianthus barbatus) by 

 observing the dark red-tinged leaves, whilst a pink 

 or a white one will have light, fresh-coloured 

 foliage. The same is true of the white and blur 

 varieties of lobelia, and the red and pink varieties 

 of fuchsia ; difference may be detected between the 

 leaves of differently coloured antirrhinums. 



Fourth and finally, with regard to insect selection, 

 I believe that insects are more influenced by scent 

 than colour ; a white, scented alyssum will attract 

 more bees than a scentless blue one, and that, too, 

 in broad daylight. I suppose no flowers receive 

 more individual visits from insects than the ivy, 

 honeysuckle (Lonicera periclymenum), and the lime 

 (Tilia), all of which have inconspicuous flowers and 

 strong scents. H. St. A Ar.nKR. 



