2l6 



NATURE 



[Jan, 9, 1879 



law is furnished by Polyi^oniiftt amphibium. Kerner shows 

 thajt the nectaries of this plant are entirely unprotected 

 against the incursions of "unbidden guests." When 

 growing in water this is no disadvantage, because none 

 but flying insects can reach the flower. But when grow- 

 ing on land the nectar would be liable to be rifled by 

 small creeping insects that would carry it away without 

 performing any compensating service to the plant, and 

 in such circumstance 5 an innumerable quantity of glan- 

 dular hairs make their appearance on the epidermis of 

 the leaves and stem which eflfectually bar the way against 

 the unwelcome visitors. " If the ground on which a 

 Polygonum has grown for years in dryness, so as to have 

 become covered with these trichomes, again be flooded, 

 and the stems and peduncles again therefore be encircled 

 with water, the trichomes with their viscidity disappear, 

 and the epidermis again becomes smooth and even." I 

 find this statement difficult to reconcile with a dictum laid 

 down further on in the volume— and, as it appears to me, 

 laid down hastily without sufficient warrant — that "the 

 so-called process of ' adaptation ' is never a direct one, 

 never comes simply in response to a want. In other 

 words, external conditions can never occasion an inhe- 

 ritable change of form, whether advantageous or the 

 contrary, can neither determine the development of an 

 organ nor its abortion." 



Although glandular hairs or viscid secretions are the 

 most common contrivances for preventing the access to the 

 nectary of useless insects, they are by no means the only 

 ones. The same object is attained by the prickles which 

 cover the upper portion of the stem or the peduncles, and 

 the spines into which the involucre of many Compositae 

 is converted. The waxy or even the glabrous epidermis 

 in some plants prevents creeping insects from reaching 

 the flowers. Even the latex or milky juice of such orders 

 as Euphorbiaceae, Convolvulaceas, and Cichoriaceae is 

 pressed into the service. Kerner placed various kinds of 

 ants on plants that were full of milky juice, such as the 

 common lettuce. No sooner did they reach the upper- 

 most leaves or peduncles than their feet cut through the 

 tender epidermis of those parts, causing the latex to flow, 

 which immediately glued the little animals to the stem so 

 that they were totally unable to escape, and most of them 

 miserably perished. The extra-floral nectaries, on the 

 leaves or other parts of the plant, of Viburnum timis 

 and opuluSy Impatieris bicornis, and many Leguminosae, 

 serve a similar purpose of diverting creeping, but not 

 winged insects from the flower ; since an insect crawling 

 up the stem would always reach these secretions of nectar 

 before the flower. 



Some plants have to be protected from animals of a 

 larger size, ruminants and other herbivorous quadrupeds. 

 Some are altogether so protected by their prickly stem 

 and leaves, or by the nauseous or unwholesome secretions 

 of their tissues. But unpalatable secretions are much 

 more common in the petals than the leaves ; and with 

 many plants the leaves are eagerly devoured by grazing 

 animals or by caterpillars, while the flowers are left 

 entirely untouched. While the comparatively large size 

 of the flowers of alpine plants no doubt has for one object 

 the attraction of hymenoptera and lepidoptera from a 

 distance, the large area occupied by them in comparison 



to the leaves — the very character which renders many of 

 them such favourite ornaments of our rockeries and 

 flower-beds — doubtless also serves to protect them from 

 destruction by goats and other mountain quadrupeds. 



Space does not allow me even to refer to many other 

 singular and interesting relationships pointed out by 

 Prof Kerner. It is of course quite possible that further 

 examination may modify some of his conclusions in their 

 detail. For example his belief that the main object of 

 the viscid secretion on the leaves of Pinguicula is to 

 prevent the access of creeping insects to the flower hardly 

 appears consistent with the fact that most species of the 

 genus flower early in the spring, while the secretion con- 

 tinues its activity through the summer and autumn. But 

 the book is a perfect mine of original research, and is 

 indispensable to all who are interested in the many 

 problems connected with the fertilisation of flowers. 



Dr. Ogle's translation is, with but little exception, easy 

 and graceful. His editorial notes are useful, and he has 

 adopted the praiseworthy practice — since the work is 

 intended for non-scientific as well as for botanical readers 

 — of explaining in foot-notes the meaning of technical 

 terms used by the writer. In a future edition this practice 

 might with advantage be extended. Such a term as 

 " epiblasteme " does not carry its own meaning with it ; 

 and even botanists not well read up in recent literature 

 would be puzzled by it. Or perhaps a glossary would 

 be more useful. Three large-sized lithographic plates 

 crowded with detail add greatly to the lucidity of the 

 descriptions. Alfred W. Bennett 



FLAMMARION ON DOUBLE STARS 

 Catalogue des J^toiles Doubles et Multiples en Mouvement 

 relatif certain. Par Camille Flammarion. (Paris : 

 G. Villars, 1878.) 



N this compact volume of less than two hundred 

 octavo pages M. Flammarion has collected together 

 the large number of measures of double and multiple 

 stars, exhibiting change in the relative positions of the 

 components, which have been made by various observers 

 since the time of the father of double-star astronomy, Sir 

 W. Herschel. Those who have been occupied in the 

 study of this branch of the science will be well aware of 

 the difficulty and trouble attending the preparation of a 

 complete history of any of these objects from the measures 

 being scattered through a great many astronomical works, 

 some of them not always easily accessible, and M. Flam- 

 marion has not yet attached his name to any volume which 

 js likely to compare with the present one in usefulness. 



The author's authorities are about one hundred in 

 number, and he refers to them by abbreviations, a list of 

 which precedes his catalogue, but it is to be regretted 

 that he has not also prefixed the titles of the volumes 

 whence the various measure s have been taken, and the 

 more so as there are indications that the original authori- 

 ties have not been invariably consulted. Thus a number 

 of Capt. Jacob's measures made with the Lerebours 

 equatorial at Madras and published in the first catalogue 

 in the volume of Observations 1848-52, are omitted in 

 M. Flammarion's lists, though he has others which appear 

 in the second catalogue in the same volume, formed after 

 the substitution of a new object-glass. In the case of 

 rr Lupi, where he regrets "que les dtoiles australes soient 



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