572 



SCIUN'CE. 



[Vol. VIII., No. 203 



tion of gases through stomataand lenticils is given 

 in lecture V. It has long been known that under 

 certain conditions some plants absorb oxygen : 

 this is most markedly true of fungi ; and Profes- 

 sor Vines states (p. 76) that it appears that the 

 power of absorbing this gas is possessed by all 

 plants, sustaining this conclusion by the experi- 

 ments of Wolkoff and Mayer on seedlings, those 

 of De Saussure, Oudemans, and others on germi- 

 nating seeds, and of De Saussure on many flowers. 

 It also appears, that, if roots are not supplied with 

 oxygen, the plant soon becomes unhealthy, and 

 ultimately dies. Portions of plants which contain 

 chlorophyl abundantly, absorb oxygen in darkness, 

 while this is given off during their exposure to 

 sunlight. All green portions absorb carbonic acid 

 in sunlight. Ammonia also is taken from the 

 atmosphere, as has been shown by Ville ; but free 

 nitrogen is apparently not thence absorbed, the 

 presence of this gas in the cell-sap being account- 

 ed for by its solubility in water. 



Lecture VI. is on the movement of water in 

 plants. A very clear account of this phenome- 

 non is given, the circulation being regarded as 

 passing mainly through the cell-walls of the ligni- 

 fied tissues. Transpiration, or the exhalation of 

 watery vapor from the leaf surfaces, is treated of 

 in the seventh lecture, and the food of plants in 

 the eighth. 



The next six chapters are devoted to the metab- 

 olism of plants, — the changes which materials 

 undergo in the tissues under the influences of 

 light, heat, chemical afiSnity, etc. ; and these are 

 perhaps the most valuable parts of the book. 

 Here the discussion begins with the consideration 

 of the formation of non-nitrogenous organic sub- 

 stances, principally starch ; then that of nitroge- 

 nous substances, collectively termed ' amides,' and 

 of the function of chlorophyl, which is concisely 

 stated to "absorb certain rays of light, and thus 

 enables the protoplasm with which it is intimately 

 connected to avail itself of the radiant energy of 

 the sun's rays for the construction of organic sub- 

 stance from carbonic acid and water." A sum- 

 mary of what is now known of the metabolic pro- 

 cesses is admirably stated on pp. 325-328 : and an 

 instructive table, showing the income and expen- 

 diture of matter and energy, is given. The energy 

 is entirely referable to the absorption of light by 

 the chlorophyl, and to heat. 



Lecture XV. is devoted to the phenomena of 

 growth ; and the following six chapters, to irri- 

 tability, which is thus minutely described, and 

 the forces inducing its manifestation fully dis- 

 cussed. In the last two chapters the subject of 

 reproduction is treated ; and here may be found a 

 resume of present knowledge of the development 



of spores and seeds in the various divisions of the 

 vegetable kingdom, the phenomena of hybridi- 

 zation, of parthenogenesis, and of variation. The 

 closing sentence is, "Evolution is no longer a 

 matter of chance, but is the inevitable outcome of 

 a fundamental property of living matter." 



At the close of each chapter of this most valua- 

 ble book, copious references to the bibliography 

 of the subjects treated are given ; but, for some 

 reason not apparent, these are only to the works 

 cited, and, except in a few instances, not to pages. 

 Had these been added, it would have greatly 

 facilitated the work of students who desire to 

 pursue the study further. A very extensive index, 

 arranged not only by subjects, but also by authors 

 quoted , is appended. 



CHALLENGER REPORTS. 



The Challenger cephalopods were at first placed 

 in the hands of Professor Huxley, whose numer- 

 ous engageiaents finally obliged him to decline 

 the work, with the exception of a special investi- 

 gation into the genus Spirula. Mr, William 

 Evans Hoyle, who was intrusted with the work 

 by Mr.. John Murray, has devoted the report now 

 under consideration chiefly to systematic work, 

 but expresses his intention of preparing a supple- 

 mentary article on the anatomy of those speci- 

 mens which are available for this purpose. He 

 alludes to the fact, that, since the return of the 

 Challenger, marine explorations have been so 

 energetically prosecuted, that no less than five 

 genera, new when obtained by the Challenger, 

 have since been described from the collections of 

 the U. S. steamers Blake and Albatross, etc. Mr. 

 Hoyle has been favored with the assistance and 

 friendly advice of Professor Steenstrup, and has 

 compared with the specimens of the fine collec- 

 tion at Copenhagen all the critical Challenger 

 species, thus insuring a double authenticity for 

 the determinations of the report. The latter com- 

 mences with an excellent synopsis of the species 

 of recent cephalopods, with references to the 

 places where they are figured and described. The 

 Challenger collection contains seventy-two species 

 of thirty genera. Of these, thirty-two species and 

 four genera were new to science. For one of 

 these, Amphitritus, possessing the unique feature 

 of having the mantle fused with the siphon in the 

 median line, so as to form two openings into the 

 branchial cavity, a new family has seemed neces- 

 sary. None of the giant squids were obtained ; as, 

 indeed, the means for capturing such animals in 

 their native haunts have not yet been devised. 



Report of the scientific results of the exploring voyage of 

 the Challenger. Vol. xvi. : Zoology. London, Government, 

 1886. 4". 



