Apbil, 1902.] 



KNOWLEDGE 



77 



" windows " for real openings the captives exhaust them- 

 selves in vain efforts to regain their liberty aiid are 

 ultimately precipitated into tiio depths of the pitcher. 



Tho flowers of the ox-eyo daisy and the feverfew are 

 very much alike, and this was adduced by tlio lat« 

 Mr. Grant Allen as a possible case of mimici-y. But 

 tho ])robabilitv is that in this iust<»ncc the resemblance 

 is merely homomorphic. Tho coloui-s of flowers arc 

 distinctive as well as atti'active. Where two species of 

 plant grow together and are in blossom at the same time 

 it is to their disadvantage to have the flowere of the 

 one mistaken for those of the other. To secure cross- 

 fertilisation it is needful that the insect visitors pass 

 from one flower to another of the same species, other- 

 wise the pollen will bo conveyed to the stigmas of the 

 wrong species. It is of importance tliat the fertilising 

 agents should bo able readily t-o distinguish difl'crcnt 

 flowers, and this is no doubt one reason for the diversity 

 of their colours, shapes and odours. This circumstance 

 must operate as a check against the production of 

 mimetic blossoms; it will not, however, prevent flowers 

 from acquiring a likeness to any object other than a 

 flower. 



Mimetic resemblances are much more numerous 

 among fruits and seeds than in flowers. A very curious 

 example is Ophicaryun paraJuruni, the snake-nut of 

 Demerara, inside which is the coiled embryo resembling 

 a small snake. Among others mentioned by Lord 

 Avebury are Tricosanthes anguina, the pod of which 

 assumes a snake-like guise; Scurpiurus vermiculafa, with 



Fi8. 8. — Mimetic Seeds. 



pods in the form of a wonn or caterpillar ; S. suhvillom 

 •Dd liiserrula peltciniis!, where the resemblance is to a 

 centipede and certain lupines with spider-like seeds. 

 The seeds of Abrus ^^rffa^or/u.s, Martynia diandra, 

 Jalropha, the castor oil plant and the scarlet runner 

 mimic certain beetles. The presence of a caruncle repre- 

 senting the head of the insect lenders the imitation 

 more complete; this structure takes no part in 

 germination, and Kerner is of opinion that it prevents 

 the ants from attacking the substance of the seeds which 

 they dra^' about from place to place. The ox-tongue 

 and cow-wheat have worm-like seeds, and several plants 

 have fruits difficult to distinguish from littlo pieces of 

 dry twig. Tho jet-black, shining seeds and achcnes of 

 Detphinnm, Hdlehorug, Junnis, Atriplex, Puly(joninn, 

 etc., are easily mistaken for beetles; tho brightly 

 coloured seeds of Iris Germanica aie also in all 

 probability mimetic. 



Tho beautiful glossy scarlet and black piebald seeds 

 of .Virus known as rosary beans perhaps escape 

 destruction through birds mistaking them for some 

 nauseous insect gaudily attired in warning colours. But 

 from tho manner in which the seed vessels of IrU and 

 Abrus dehisce and expose their seeds the brilliant colours 

 of the latter would appear to subsei-ve dissemination 

 rather than protection. Such hard seeds are probably 



dispei-sed through tho agency of insectivorous birds, 

 which seizo them in mistake for their more legitimate 

 prey. According to Lord Avebm-y the beans of Abrus 

 mimic tho beetle Artemis circuinustd. The smaller seeds 

 known as crab's eyes aro coloured in an analogous 

 manner. These cases are tho less surprising if we have 

 legard to the fact that the great majority of dry fruits, 



Fio. '.».— Piebald Beans of Abrus. 



though green while growing, become black or brown 

 when they fall to tho ground, so that their general tint 

 corresponds with their surroundings and tends to 

 concealment. 



THE ARCETRI OBSERVATORY, FLORENCE. 



By W. Alfred Park. 



The beautifully illustrated brochure* on the Arcetri 

 Observatory, just issued by its Director, Prof. Antoion 

 Abetti, draws attention to an institution which, standincr 

 as it does on the classic ground dedicated to the memory 

 of Galileo, and overlooking the broad valley of the Arno, 

 possesses an interest equalling that of many a lart^er 

 and better known observatory. As far back as the 

 year 1774. Florence, which could justly claim to be con- 

 sidered the intellectual capital, as it was nearly a century 

 later, if but for a short period, the political capital of 

 Italy, possessed a small observatory divided into an 

 astronomical and a meteorological "department, which 

 formed part of the building of the Museum of Science and 

 Natural History, occupying a wing of the Pitti Palace, in 

 the Boboli Gardens. The history of this museum is in 

 itself of extreme interest, as it was established under the 

 nilers who succeeded Ferdinand II., Grand-Duke of 

 Tuscany (1621-1670), during whose reign was founded its 

 more celebrated predecessor, the famous Accaclemia dd 

 Cimento, itself called into existence by the works of 

 Galileo and his school. 



Among the earlier astronomers who worked at the 

 Florence Observatory may be mentioned De-Vecchi, who 

 died in 1829, and Pons, celebrated for his cometary 

 researches. Amici, who succeeded Pous in the director- 

 ship, was a noted physicist and optician of his time, and 

 did much to re-establish for Florence the reputation it had 

 enjoyed in Galileo's time as a centre for the construction 

 of optical instruments. Amici's objectives were justly 

 celebrated, one of his best and, at that time, one of the 

 largest in existence being tho excellent ll-.5-inch object- 

 glass still in use at the Obs(.'rvatory. The chief astronomical 

 activity of Florence, however, may be said to have 

 commenced with Donati, who, towards the end of 18.59, 

 succeeded Amici as Director of the Observatory, and 

 through whoso exertions principally the astronomical 

 dc|)artment was transferred to its present more favourable 

 position on the hill of Arcetri, to the south of the city 

 and quite close to the villa where Galileo died. Donati, 

 who commenced the construction of the new observatory 

 building in 1869, had already become universally known 



• " L'osservatorio Astronomico di Arcetri ; Appunti Storiei ed 

 lllustrazioni." Firenze, 1901. 



