284 



KNOWLEDGE 



[December 2, 1895. 



same temperature, there will be no dark line produced. 

 The absorption of the light ■wUl take place as before, but 

 as the light given out by the second flame is of the same 

 sort and of the same intensity, it simply takes the place of 

 the absorbed light, and the result is that no dark line 

 occurs. If light, forming a continuous spectrum, but 

 coming from a source at a lower temperature than an 

 interposed sodium flame, be observed with a spectroscope, 

 the yellow D lines are seen as bright lines on a back- 

 ground formed by the continuous but less bright spectrum. 

 Kirchhofl' concluded from his experiments that the dark 

 D hne in sunlight was caused by the presence of sodium 

 vapour in the atmosphere of our luminary at a lower 

 temperature than the source of light. This conclusion 

 was strengthened when he observed dark lines coinciding 

 with the bright lines given out by various metallic vapours, 

 and in this way the presence of iron, nickel, calcium, 

 magnesium and other metals was detected in the solar 

 atmosphere. The lines C and F in the solar spectrum 

 were proved to be due to hydrogen, and no fewer than 

 four hundred and fifty of the solar dark lines have been 

 identified with the bright lines given out by iron. On the 

 other hand, the lines which would be produced by the 

 absorption due to mercury, gold, aluminium, lead, tin, and 

 some other elements are not found in the solar spectrum, 

 and their absence seems to point to the conclusion that 

 these elements are lacking in the sun's absorbent 

 atmosphere. 



MISTLETOE AND MISTLE THRUSH. 



By Ge.\ha5i W. Murdoch. 



THE mysteries which have gathered round the 

 mistletoe plant, the llscuiu album of botanists, 

 have struck their roots deep in the romance of 

 folk-lore, in the evolution of cults and supersti- 

 tious ceremonial, far beyond even the deep 

 woodland ritual of the Druid priest. Even the most 

 learned of philologists of the present day are not agreed as 

 to the origin of the word. It fills, too, no inconsiderable 

 apace in realms of poetry. Our great Elizabethan drama- 

 tists have employed it and its imaginary properties and 

 parasitical ways to point their morals. Under its boughs, 

 at the merry Christmastide, many a life's romance, many 

 human comedies and even tragedies, have received their 

 first meaningless or passionate note of inspiration. In 

 this article we must not be tempted, beyond this casual 

 allusion, into a consideration of the mistletoe in any of 

 these fascinating fields of speculation. Our purpose is to 

 point out certain purely scientific phenomena in connection 

 with the plant and the mistle thrush {Turdxs riscirorus), 

 about which much controversy has been waged, and in 

 connection with which considerable ignorance still prevails, 

 even among botanists and ornithologists. For instance, 

 in one of the standard German works on sylviculture 

 (" The Waldschutz of Kauschiuger," by Hermann Furst), 

 the statement is made that the mistletoe plant "probably" 

 owes its wide extension and reproduction to thrushes, 

 which eagerly consume its berries, and " in cleansing 

 their beaks from the sticky flesh of the fruit, leave a 

 portion of it on the bark of the tree along with some of the 

 seeds contained in it."' That is not so, as we shall show, 

 and the elements of science romance are interwoven with 

 this very theory of seed propaganda and of specific motbis 

 operamli. Curiously enough, the ancient theory which 

 found favour with Aristotle, Pliny, .Elian, Phile, and 

 others, and which the poets followed blindly and enlarged 

 upon in metaphor form, was rudely assailed by Lord 



Bacon in his " Sylva Sylvarum " (1635), and even more 

 vigorously ridiculed by the very sceptical Sir Thomas 

 Browne in his " Pseudoxia Epidemica " (1672), but is now 

 established as true beyond the shadow of a doubt. The 

 truth has been revealed by the labours of field naturalists 

 and observant botanists working on the very inductive 

 lines of reasoning that Lord Bacon is popularly credited 

 with having " founded," and which undoubtedly were 

 successfully employed by Sir Thomas Browne in exposing 

 many " Vulgar Errors." Lord Bacon ventures upon 

 reasons for discarding the ancient theory, which are alto- 

 gether fallacious. The passage will be found on pages 139 

 to 112 of the edition referred to, the old spelling and 

 punctuation and use of capital letters being followed. 



" We finde no Super-plant that is a Formed Plant, but 

 Misseltoe. They have an idle Tradition, that there is a 

 Bird, called a Missel-Bird, that feedeth upon a Seed, which 

 many times shee cannot digest, and so expeleth the whole 

 with her Excrement which falling upon a Bough of a Tree, 

 that hath some Rift, putteth forth the Misseltoe. But 

 this is a Fable : For it is not probable, that Birds should 

 feed upon that they cannot digest. But allow that yet it 

 cannot be for other Reasons : For First it is found upon 

 certaine Trees : And those Trees beare no such Fruit, as 

 may allure tbat Bird to sit, and feed upon them. It may 

 be that Bird feedeth upon the Misseltoe-Berries, and so is 

 often found there : Which may have given occasion to the 

 Tale, But that which maketh an End of the Question, is, 

 that Misseltoe hath beene found to put forth under the 

 Boughes, and not [onely] above the Boughes : So it cannot 

 be any Thing tbat falleth upon the Bough. Misseltoe 

 gi-oweth chiefly upon Crab-Trees, Apple-Trees, sometimes 

 upon Hasles ; And rarely upon Oakes ; The Misseltoe 

 whereof is scounted verie Medicinall. It is ever greene, 

 Winter and Summer ; And beareth a White Glistering 

 Berry : And it is a Plant, utterly differing from the Plant, 

 upon which it groweth. Two things therefore may be 

 certainly set down. First that Seeper-fetation must be by 

 Abundance of Sap, in Bough that putteth it forth : 

 Secondly, that that Sap must be such, as the Tree doth 

 excerne, and cannot assimilate For else it would goe into a 

 Bough ; And besides, it seemeth to be more Fat and 

 Unctuous, than the Ordinary Sap of the Tree, Both by the 

 Berry which is Clammie ; And by that it continueth greene, 

 Winter and Summer which the Tree doth not.'' 



The basis of Lord Bacon's objections to the ancient 

 theory, and, as we shall show, correct theory, is that " it 

 is not probable birds should feed upon that they cannot 

 digest," the fact being that bu'ds do feed on " that they 

 cannot digest," but which is used as an aid to digestion. 

 In the palmy days of falconry in this country, falconers 

 knew this secret of nature, and more than one reference to 

 it will be found in the dramas of the period. Thus 

 Webster, for instance, in the great tragedy of The White 

 Devil, Act III., Scene 1 — 



" TiTTORiA CoROiiBOXA : Surely, my loi'd.<, tliis lawyer here liatli 

 swallowed 

 Some potheenries' bills or proclamations, 

 ,Vnd now the hard and uudigestible words 

 Conic up, like stones we used to give hawks for physic." 



The fact is that it is a necessity for birds (the ostriches 

 in particular) to swallow hard bodies, which remain in the 

 pyloric region of the stomach and there play the part, as 

 regards food, of masticatory organs. But as far as many 

 seeds are concerned, it is notorious that they do pass 

 through the organic system, not only of birds but of 

 mammals, in an undigested form, and without their vital 

 fructifying functions being destroyed. It is, of course, 

 notoriously so with the seeds of the mistletoe as swallowed 



