618 



SCIENCE 



[N. S. Vol. XXVII. No. 694 



The Use of Complex Quantities in Alter- 

 nating Currents: G. W. Patterson, Uni- 

 versity of Michigan. 



Physical Research at a Mountain Observa- 

 tory: G. E. Hale, Mt. Wilson Observa- 

 tory. 



Some Curious High-temperature Phe- 

 nomena: C. E. Mendenhall, University 

 of Wisconsin. 



Alpeed D. Cole, 



Secretary 

 Vassae College 



SCIENTIFW BOOKS 

 The Origin of a Land Flora: A Theory lased 

 upon the Facts of Alternation. By F. O. 

 Bower, Sc.D., F.E.S., Eegius Professor of 

 Botany in the University of Glasgow. With 

 numerous illustrations. 8vo, pp. xii + 727. 

 Macmillan and Company, Limited. St. 

 Martin's Street, London, 1908. 

 The author of this book is well known to 

 American botanists as the writer of many 

 lucid articles, and especially as the propounder 

 of a very helpful theory as to the nature of 

 the flower and its relation to the remainder of 

 the sporophyte. When Professor Bower pub- 

 lished his "theory of the strobilus " {Annals 

 of Botany, Vol. VIIL, 1894, p. 343) he made 

 a contribution to morphology which at once 

 marshaled the floral and foliage structures of 

 higher plants in accordance with the doctrine 

 of evolution, and destroyed the time-honored 

 theory of the metamorphosis of foliage leaves 

 into the perianth and essential organs of the 

 flower. In the light of this theory the origin 

 of the flower is no longer the hazy, although 

 plausible impossibility of the older text-books. 

 That he swept away along with much accom- 

 panying rubbish, and in its place gave us an 

 explanation which has the double merit of 

 agreeing with observed facts, as well as being 

 biologically possible. Now the author who 

 gave us a rational theory of the origin of the 

 flower appears with a volume devoted to the 

 origin of the terrestrial habit in plants, or as 

 he puts it in the title of his book— the origin 

 of a land flora— and we may predict for this 



later theory a history equally successful with 

 the former. 



The volume consists of forty-seven chapters, 

 divided into three parts, the first (of twenty 

 chapters) being devoted to a " statement of 

 the working hypothesis," the second (of twenty 

 chapters, also) including a " detailed state- 

 ment of facts," and the third (of seven chap- 

 ters) devoted to " conclusions." Starting with 

 the accepted doctrine of biologists that ani- 

 mal and plant life originated in the water, 

 he shows that it is the sporophyte generation 

 which becomes terrestrial, while the gameto- 

 phyte is wholly aquatic, or at best still greatly 

 dependent upon an abundant supply of water. 

 His statement (p. 244) is so clear that we 

 quote it here verbatim : " In respect to their 

 whole life-cycle the Archegoniatae may be 

 said to show an amphibial existence, the 

 aquatic and the terrestrial characters being 

 reflected in its two alternating phases. The 

 gametophyte is as a rule delicate in texture, 

 without intercellular spaces in its tissues, or 

 a fvilly developed water-conducting system, 

 while its sexual organs only become functional 

 on their rupture in water outside the plant- 

 body : the gametophyte thus proclaims its ulti- 

 mate dependence on external fluid water as 

 thoroughly as an alga. The sporophyte, on 

 the other hand, is a characteristically sub- 

 aerial body; this is shown by its more robust 

 habit, its effective ventilating system, and its 

 vascular strands for the conducting function 

 seen in the higher forms : its final result, the 

 maturing and dissemination of spores, is nor- 

 mally carried out binder circumstances of dry- 

 ness. All these features mark it as an essen- 

 tially terrestrial phase." 



In Chapter V. the author discusses the cyto- 

 logical diflerences between the gametophyte 

 and sporophyte first distinctly pointed out by 

 Strasburger in 1894, accepting chromosome- 

 reduction as marking the end of the sporo- 

 phs^te generation and the beginning of the 

 gametophyte, and chromosome-doubling as the 

 end of the gametophyte generation and begin- 

 ning of the sporophyte. By applying, this test 

 the beginnings of an alternation of genera- 

 tions may be recognized cytologically in the 



