280 



♦ KNOWLEDGE ♦ 



[Oct. 3, 1884. 



as the thaumatrope. It consists of a circular disc 

 of stout white card, upon one side of which we have shown 

 a drawing of a mouse, and on the other one of a cage, 

 which must be drawn upside down, as referred to the first 

 figure. At the sides of the discs are two strings, which 

 are held between the forefinger and thumb of each hand, 

 and twirled rapidly round, the eflfect being that we see the 

 mouse in the cage. We may, of course, draw in the same 

 way a man on one side and a horse on the other, a tight- 

 rope dancer and his rope, and so on. We may add that if 

 the strings by which the card is twirled be not on a dia- 

 meter, so that the card does not rotate about its principal 

 axis, the figures will be displaced, so that we may have our 

 mouse either on his cage or under it instead of in it, by a 

 suitable arrangement. 



GRASS OF PARNASSUS. 



By Grant Allen. 



VS we have been going in lately for a course of coin- 

 cidences in Knowledge, I will begin this paper with 

 a sufficiently curious one which happened to me during my 

 summer holiday the other day in Norfolk. I had walked 

 over by the breezy clifl' path from Cromer to Beeston 

 Common, and had been diligently investigating for a whole 

 sunny afternoon the exceptionally rich boggy flora of that 

 pretty bit of deep, waterlogged moorland scenery. The 

 ground, for acres together, was covered with pale yellowish- 

 green rosettes of tufted butterwort, and tall lush trefoils 

 of beautiful buckbean, and golden clusters of belated marsh 

 marigolds, blossoming still out of due season. But the 

 prettiest flower in all the wide stretch of swampy vege- 

 tation was the white grass of Parnassus, whose exquisite 

 veined blossoms starred the soil on every watery patch in 

 the most astonishing jjrofusion. I stood for a long time 

 watching the flies buzzing idly around them, and then 

 picked a number out of pure wantonness, to take home 

 with me as an appropriate tribute to a great poet who was 

 staying in the neighbourhood. As soon as I got back, I 

 put the drooping flowers in water, and proceeded to ojien 

 the letters which were waiting for me on the parlour table. 

 The first one at which I looked had been forwarded to me 

 by the Editor of Knowledge, and it ran as follows : — 



SiK, — Would Mr Grant Allen or any of your botanical con- 

 tributors kindly state what useful object (if any) is attained in 

 Pamassia palustris by the very curious development of its imperfect 

 stamens, and oblige A Student of Botany ? 



Clearly this was the finger of fate. Farnassia jmlustris, 

 with its abortive stamens, was staring me in the face from 

 the glass in front of me ; and I had been spending all the 

 afternoon in watching the flies in the very act of being 

 taken in by the deceptive staminal organs in question. 



First of all, then, let me begin by briefly describing this 

 grass of Parnassus. It is a marsh-land plant, of the saxi- 

 frage family, having some affinities with the sundew, but 

 even more (as has been recently shown) with the true saxi- 

 frages and chrysospleniums. From a small tuft of heart- 

 shaped, glossy-green, radical leaves, a rather tall scape rises 

 abruptly, enclosed half-way up by a curiously clasping leaf, 

 and bearing at its summit a single, large, snow-white flower. 

 The blossom has five petals and five perfect stamens ; but the 

 place of the five inner stamens (which occur normally in 

 the saxifrages) is taken by some very strange abortive 

 organs, at the base of the petals, split up into eight or ten 

 short, spreading filaments, and terminated at the end, 

 where the anther ought to be, by a little, yellow, shining, 

 globular gland. So very bright and glassy are these tiny 



balls that they look for all the world exactly like a drop of 

 liquid ; and the imitation goes so far that even when one 

 has touched them with one's finger it is difficult to believe 

 they are not really glistening drops of limpid honey. These 

 are the organs whose use and function " A Lover of 

 Botany" wishes to learn about. 



It was Hermann Muller who first pointed out the true 

 meaning of these odd staminodes. They are really decep- 

 tive organs, which attract flies and other insects by the 

 fallacious appearance of a store of honey. " The yellow 

 knobs placed at the ends of the hairs," saj-s Miiller, " look 

 so extremely like drops of fluid that it needs close examina- 

 tion to convince one they are thoroughly dry. An observa- 

 tion of my son's proves that even flies are taken in by the 

 appearance of liquidity. He saw from a short distance a 

 specimen of ErintaJis nemorum trying to lick these bodies 

 for a long time, until at last it flew away on his coming 

 closer." I myself observed exactly the same thing several 

 times over at Beeston Common ; the flies alighted on the 

 disk of the pistil, and tried hard to lick honey, over and 

 over again, from the small, dry glassy bulbs. 



We have thus, as Miiller remarks, in grass of Parnassus 

 an excellent example of a deceptive flower, which deludes 

 the foolish flies by ofTering them a number of conspicuous 

 but sham drops of honey. At the same time, the deception 

 is not quite absolute, for the staminodes have a broad base, 

 which secretes two small lots of nectar in two shallow 

 depressions on its inner side. This honey is suflacient to 

 prevent the flies from altogether discovering the im- 

 position, and giving up the hunt in futvire as useless. 

 After long and vain attempts to find nectar in the decep- 

 tive glands, they are at last rewarded for their pains by a 

 much smaller store laid by in the depressions at the base 

 cf the staminodes. 



The perfect stamens lie at first with their anthers coiled 

 up over the immature pistil, and they ripen slowly, one at 

 a time, each anther as it begins to shed its pollen bending 

 over outward, so as to come into contact with the head and 

 shoulders of the fly who is busily hunting for nectar among 

 the false staminodes. As soon as all the stamens have shed 

 their store, the stigmas of the pistil become fully mature, 

 so that the flies, in visiting the younger flowers, collect 

 pollen on their heads and legs, which they finally rub oiT 

 upon other blossoms in the second or female stage. This, 

 of course, is a common and familiar device for ensuring the 

 benefits of cross-fertilisation. 



It is worth notice that such deceptive flowers occur most 

 especially among the species which lay themselves out to 

 attract the true flies (Diptera). Flies appear to be far 

 more stupid and unintelligent than bees, sand-wasps, moths, 

 and beetles, and therefore more liable to be taken in by 

 simple forms of floral deception. Thus the carrion-flies are 

 imposed upon by many reddish flowers (of which the great 

 oriental Eafflesia Arnoldi may be taken as a type) — flowers 

 that imitate putrefying meat in colour and odour, and so 

 induce the flies to lay their eggs upon the surface, and 

 incidentally to cross-fertilise the alluring plants. In the 

 common English arum, again, a very small fly is tempted 

 by the odour to imprison itself behind a chevaxix-defrise 

 of hairs ; which also happens somewhat difierently to 

 another species in the long tube of the south-European 

 birthwort Muller notes other instances of pure deception 

 in Ophrys, Paris, Stapelia, and a few more flowers, every 

 one of them designed to take in various species of Diptera. 

 There can be very little doubt that this consensus of 

 condemnatory evidence points to an exceptional degree of 

 stupidity on the part of the two-winged order. 



On the other hand, the esthetic taste of the flies is dis- 

 tinctly high. The colours of the flowers which we owe to 



