Scpf. 2 2, t88i] 



NA TURE 



501 



species have long tubulai- flowers specially adapted to bees and 

 butterflies, while the yellow gentian has a simple open flower 

 with expo ed honey. Sir John also described his experiments 

 made on daphnias by illuminating a Iroigh with an exte:.ded 

 sol.v spectrum in such a way that after a given lap-e of time he 

 could isolate the portion of tlie trough illuminated by each prin- 

 cipal colnir, and count the number of daphnias in it. They 

 appeared to have a very predominant preference for the red ard 

 yellow and greenish yellow and green. He also found, contrary 

 to the conclu ion of M. Paul Bert, that Ihey clearly pirceive the 

 ultra violet rays. 



Sir John Lu*^]! ocU read a paper On the Mode in -which the Seed 

 of St i pa buries itself in the Ground. — One of the most interesting 

 parts in botany, he said, was the consideratian of the reasons 

 which led to the different forms, colours, and structures of seeds ; 

 and it was, he tliought, pretty well made out that a large pro- 

 portion of those might be accounted for either as serving to 

 protect the seed or to assist in its convtyance to a place suitable 

 for its growth. If the seeds of trees fell directly to the "r. und 

 it was obvious that veiy few of them would have a chance of 

 cronino'. It was an advat tage to them, therefore, of which 

 many availed themselves, to throw' out wings, in consequence of 

 which the wind w-afted them lo a greater or Ie<s distance. 

 Others, such as the whole tribe of nuts, being edible, were 

 carried about by beasts and birds, and though some were sacri- 

 ficed, others survived. Fruits, again, in consequence of their 

 sweetness, were carried about by animals, which, after partaking 

 of the fleshy portion, dropped the seeds themselves. Many 

 seeds were covered with hooks, ant thus, adhering to the wool of 

 sheep and other animals, were carried to greater or less distances. 

 Others, like those of our common dandelion, were provided with 

 fairy parachutes, and were thus borne away by the wind. Others 

 again, like some of the violets, geraniums, vetches, brooms, 

 cucumbers, cardamine, oxalis, and others, had beautiful and 

 varied contrivances, by which they actually threw the seeds to a 

 distance, in some cases of more than 20 feet. Others, again, 

 were enabled to penetrate the earth, and thus sow themselves in 

 the ground. In one of our English clovers, Trifolium suhter- 

 raneuni, after the flower had faded, it turned downward^, and 

 buried it-elf in the ground. The ground nut of the West Indies, 

 and moie than one species of vetch, had a similar habit. In the 

 Erodiums or Crane-bills, the fruit is a capsule, which opens 

 elasticallv, and as in the case of the allied geraniums, sometimes 

 threw seeds to some little di-Unce. The seeds themselves were 

 spindle-shaped, hairy, and produced into a twisted awn. The 

 number of turns on the awn depended upon the amount of 

 moisture. Mr. Rowe, to whom they were indebted for an ac- 

 count of their mechanism and mode of action, said if a seed he 

 laid upon the ground, it remained quiet as long as it was dry, 

 l">ut so soon as it was moistened the outer side of the awn con- 

 tracted, and the hairs surrounding the seed moved outwards, the 

 result of which was to raise the seed into an upright posi'ion. 

 The awn then gr.adually unrolled, consequently elongating itself 

 upwards, w th the result that if it was entangled amongst any of 

 the surrounding herbage, the seed was forced into the ground. 

 .\ still more remarkable case was that of the Stipa pennata. 

 The actual seed was small, with a sharp point, and with stiff 

 short hairs pointing backwards. The upper end of the seed 

 was continued into a fine twisted rod; then came a plain cylin- 

 drical portion attached af an angle to the corkscrew, and ending 

 in a long and beautiful feather — the whole being about a foot in 

 length. That end was supposed by Mr. Francis Darwin, to 

 whom they were indebted for a very interesting memoir on the 

 subject, to act very much in the same manner as that of Erodiiim, 

 .already mentioned. He did not doubt that the end would bury 

 itself in the manner described by Mr. Darwin, buthedrubted 

 whether it always did so. One fine day, not \on% ago, he 

 chanced to be looking at a plant of that species, and around it 

 were several seeds more or less firmly buried in the ground. 

 Tliere was a little wind blowing at the time, and it struck him 

 that the long feather awn was admirably adapted to catch the 

 wind, while on the other hand it seemed almo-t too delicate to 

 drive the seed into the ground in the manner described by 

 Darwin. He therefore took a seed and placed it upright on the 

 turf. The day was perfectly fine, and there c uld therefore be 

 no question of hydroscopic action. Nevertheless, when he 

 returned after a few hours, he found that the seed had buried 

 itself -ome little distance in the ground. He repeated the 

 obsenation several times, always with the same result ; thus 

 convincing himself that one method, at any rate, by wiiich seeds 



bury themselves is by taking advantage of the action of the 

 wind, and that the tuisted position i f the awn, by its corkscrew- 

 like movement, facilitates the entry of the seed into the gi-oimd. 

 Mr. .'\. W. Bennett read a paper On the Constancy of Insects 

 in Visiting Flo-it'crs. He said he v as not aware that attempts 

 had yet been made to determine the question whether insects 

 were altogether dif criminating in their visits to flower.s, or 

 whether on the same journey they confined them' elves exclu- 

 sively or chiefly to one species. That paper, which was the 

 result of observa'ions daring the fine weather of the last two 

 years, was intended as a contribution towards the settlement of 

 that question, obviously one < f some importance in relation to 

 the cross fertilisation of flowers by insects. Those who had not 

 made the experiment would hardly appreciate how difficult it 

 was to watch continuously for any considerable period the flight 

 of any insect. He had chosen in all cases as points of observa- 

 tion spots where a considerable number of different flowers grew 

 in profusion, and were intermixed, so that the irsect would 

 have abundant opportunity of changing its diet if so disposed. 

 In recording the number of flow ers of the same kind visi'ed by 

 an insect in the same flight, he always meant flowers at such a 

 distance from one another that the inect had to use its wings in 

 getting from one to another. In August of last year he observed 

 three different flights of the "pain'ed lady" butterfly, and it 

 settled six, three, and ten times respectively, always confining 

 itself to the same species of flower. On the same plot a hive- 

 bee paid nine successive visits to the same species of flower. 

 On another plot a bumble-bee visited the same species of flower 

 fifteen times, and another of the same species eleven limes in 

 success! )n, not touching .any other fl iwer, I ut passing over many. 

 Mr. Bennett gave further results of his observations on diflferent 

 occasions and in different parts of the c untry. In order to test 

 whether insects were guided by colcm- only when vishing flowers, 

 he watched one spot where there were white and purp'e fox- 

 gloves, but a large Intmble-bee was seen to enter sixteen of the 

 flowers regardless of colour, althi ugh to find the succession of 

 foxgloves it had to fly considerable distances over other flowers. 

 No general statement could be made as to the consistency of 

 insects in visiting the same species of flower during th; same 

 flight. A decided preference for successive visits to the saire 

 flower was uaquesiionably shown in many inst.inces, but those 

 visits did not depend on the colour of the flower only. The 

 hive-bee appeared to be by far the most constant in that 

 respect, often ab ohitely so. From their strong and rapid flight 

 and extremely ha ry covering of their abdomen, that class of 

 insects was probably the most efficient ager.t in the dissemination 

 of pollen. So far as could be gathered from rb ervation, the 

 " painted lady " and the small tortoise-shell butterflies were very 

 consistent, while the whites, the blues, and the browns were far 

 from catholic, or less discriminative in their tastes. It was open 

 to question, however, whether more than a very few flowers 

 were dependent upon butterflies for their fertilisation. At all 

 evens their visits to flowers were often only interlndes in their 

 setilements on grass, leaves, the stems of trees, or the bare 

 ground. 



Prof. O. C. Marsh of Harvard, U.S., contributed one of the 

 most attractive papers to this department. On Jurassic Birds and 

 their Allies. He detailed the results of his examination of the 

 ArchKopteryx in the Britih Mueum, the more recently dis- 

 covered specimen at Berlin, and of^ Compsognathus in the 

 Munich Museum, as compared \\\\\i the forms previously made 

 known by himself in America. His impression was that the 

 two specimens of Archoaopteryx were specifically identical, 

 although fuller evidence might prove them to be distinct. He 

 still considered that we knew little that could detei'mine how 

 or at what period birds originated. At present the four oldest 

 known birds were as distinct from one another as any birds of 

 the present day. Yet if he were asked to dislingxiish between 

 the bones of a reptile such as Compsognathus and a bird such 

 as Archa:opteryx, if broken up and mixed together, he should 

 be puzzled to do it. Prof. H. G. Seeley, in the subsequent 

 discussion, stated his belief that the British Museum Archreo- 

 pteryx was not merely specifically, but generically distinct 

 from that at Berlin. 



Dr. A. A. W. Hubrecht of Leyden gave an interesting 

 exposition of The Structure and Affinities of Proneommia, ore of 

 the valuable finds of the Challenger Expedition. Dr. Hubrecht 

 spoke in excellent English, and was listened to with much 

 appreciation. 



Mr. Forbes gave an account of his work On the Anatomy ana 



