132 



KNOWLEDGE 



[July 1, 1891. 



Cdlonjnt/iia) (Cucurbitace!*), the jalap (Iiwnuca purya) 

 (Convolvnlaceiv), Kui'lioi-hia Lathyris, the croton-oil 

 plant {Cri'tiiii 'rii/liuni). the castor-oil plant {niciniix nmi- 

 viunia), the physic nut {Jatriqiha Cuirns) (EuphorbiaceiP) ; 

 n/mnnnis riitluiitiius, Bniiiiux cntlKirticv.i, ]j. /lurganf:, xc. 



Emetic and purging seeds are not likely to be retaine<l 

 long enough in an animal's stomach to admit of their 

 germinating power being destroyed. 



Narcotic and poisonous properties are not uncommon 

 in seeds and fruits. We have marked examples of this in 

 Ativjiii, lli/ii.si;/(imiis, Andromeda, Strijchnos, and in some 

 of the Apocynace* and Umbelliferie. A seed that 

 occasions the death of any animal that swallows it might 

 be benefited by its poisonous properties if the rich soil 

 furnished by the decaying body of its victim were neces- 

 .sary for its germination. But it is hardly possible that 

 this can be the end intended in all poisonous seeds. If 

 any plant were systematically to poison the birds on 

 which it depended for dispersion one of two things must 

 happen. Either this short-sighted policy would lead to 

 the extermination of its benefactors, or the birds would 

 gradually learn to avoid its fruits. In any case the plant 

 would lose its means of dispersion, and place itself at such 

 a disadvantage in the competition with other species as 

 would in the long run lead to its own extinction. Further, 

 it must be remembered that substances poisonous to man 

 and certain other animals are without effect on certain 

 others. Thus, rabbits eat the leaves, and thrushes the 

 berries, of the deadly nightshade ; strychnine is said to 

 have no injurious effects upon monkeys. Poisonous com- 

 pounds may be formed in plants and occur as accidental 

 qualities, just hke the mineral poisons of the inorganic 

 world. It seems improliable that these poisons should 

 be produced in fruits for the purpose of destroying the 

 agents concerned in dispersion. If, however, this should 

 tiu:n out to be the case in some instances, it would after 

 all be no more wonderful than what occurs in such 

 insectivorous plants as Drosera and Dionoea. 



Birds are known to eat many poisonous fruits with 

 impunity. The fruits of the manchineel [Hippuinani) 

 contain a deadly poison, and yet certain birds in South 

 America eat them without injury, just as happens in oitr 

 own country with the scarlet berries of the honeysuckle. 

 The active principle of castor oil is not found in any part 

 of the seed except the embryo, and the poison in several of 

 the Solanacese is said to occur only in the outer covering 

 of the seed and not at all in the pericarp. All parts oi 

 Hyoscyamus are more or less isoisonous. Its popular 

 name of Henbane arises from the idea that it has a special 

 fatality for hens. This is quite intelligible on the sup- 

 position of the poison being concentrated in the outer 

 layers of the seed. On account of the trituration to which 

 the seeds are subjected m the gizzard, they are much more 

 likely to prove fatal to a gallinaceous fow'l than to other 

 birds with weaker stomachs. 



Such considerations indicate that the use of these 

 poisonous properties may be to prevent the fruits being 

 eaten by animals, which woitld so thoroughly digest the 

 seeds that their germinating power would be destroyed. 

 The development of poisonous principles in connection 

 with the fruit is probably of use also as a protection 

 against injurious insects. These are very ready to attack 

 fruits in all stages of growth ; it is quite conceivable, there- 

 fore, that the poisons in berries are primarily intended to 

 act as insecticides, and that later on they come to be of use 

 in keeping away other animals capable of injuring the 

 seeds. 



When a poisonous principle first began to be developed 

 in any particular fruit, the birds which fed on it, we should 



naturally suppose, would become gradually inured to the 

 poison until it completely lost its effect. The liking of 

 parrots for peppercorns, in all probability, is an acquired 

 taste. Immunity from particular poisons might be ac- 

 quired in the same way as we may suppose the strong 

 mandibles of the parrot have been acquired in relation to 

 hard-shelled fruits. Where poisoning occurs it would 

 seem to be accidental, and should perhaps be regarded as 

 arising from imperfect instincts, or as the inevitable con- 

 comitant of a transition stage in development towards 

 more perfect adaptation. On the same principle we should 

 also be disposed to explain the case of those Aroids whose 

 flowers, according to Delpino, poison the snails on which 

 they depend for fertilisation. 



(7V/ )ic idiitiiaccil.) 



Notifts of Boofts. 



TcU'sciipc TI'o/7r for StarJiijht Ercnimix. By William F. 

 Denning, F.E.A.S. (London, 1891, Taylor & Francis.) 

 ]\Ir. Denhing is so well known as a patient observer of 

 meteors and of comets, that a work from him on obser- 

 vational astronomy will be looked upon with special interest. 

 The plan of the book is somewhat on the lines of the late 

 Mr. Webb's ('ehstitd objects for I'miniuin Teleaenpes ; 

 though it does not profess to compete with it in the 

 detailed description of the moon or of stellar objects. One 

 naturally turns first of all to Mr. Denning's chapter on 

 meteors and meteoric observations, which contains some 

 striking pictures of detonating meteors, and of double and 

 curved meteor tracks. The meteor masses which enter 

 the air are occasionally so irregular in shape that the 

 resistance of the atmosphere as they pass quickly through it 

 drives them out of their original course. Mr. Denning says 

 that several outbursts of hght are often noted, and sometimes 

 a curious halting motion ( which must of course lie an optical 

 illusion) has been noticed. He states that he has occasion- 

 ally remarked a succession of brilliant flashes given by one 

 fireball. These flashes, though sometimes of startling in- 

 tensity, are somewhat difl'erent from the transient vividness 

 of lightning, they come more softly, and Mr. Denning 

 says that they remind him of moonlight breaking suddenly 

 through the clear intervals in passing clouds. Great 

 difi'erences are noted in the velocity of meteors ; some 

 move very slowly, while others shoot quickly across the 

 sky. These difi'erences are caused by the astronomical 

 conditions aft'ecting the position of the meteor-orbil; 

 relatively to the motion of the earth. Thus the meteors 

 of November 13tli move with great velocity (44 miles per 

 second), because they come from th'e part of the heavens 

 towards which the earth is moving with a speed of 

 18^ mOes per second, while the meteors themselves are 

 moving in nearly a contrary direction with a velocity of 

 26 miles a second. But in the case of the meteors 

 belonging to the shower of November 27th, the meteors 

 catch up the earth from behind ; their relative motion is 

 therefore extremely slow, being only about 10 miles a 

 second. On November 12th, 1790, Humboldt at Cumana, 

 in South America, saw " thousands of bolides and falling 

 stars succeed each other during fom- hours." On 

 November 12th, 1833, the shower recurred, and was 

 witnessed with magnificent effect in America. It was 

 first noted during this shower that the meteor tracks all 

 seemed to radiate from a point in the heavens ; subse- 

 quently Heis in Germany, Schmidt at Bonn and Athens, 

 Mr. R. P. Greg and Prof. Alex. Herschel in England, bv 



