436 



SCIENCE. 



[N.S. Vol,. XX. No. 509. 



eluding the Hydoeharideae. Under the 

 Glumiflorse the grasses (Graminese) are de- 

 scribed as having a solitary carpel, which is 

 certainly an error for the three-styled genera, 

 and probably so for those with two styles, 

 flackel's arrangement is followed. Curiously, 

 in the sedges (Cyperacese) the carpels are de- 

 scribed as ' three or two.' How these two 

 views as to the nature of the pistil can be 

 harmonized is difficult to make out. 



The palms and aroids (Principes and 

 Spathiflorse of Engier) are united into the 

 ' series ' Spadiciilorse. A curious typograph- 

 ical error occurs on page 250 (and is repeated 

 on page 256) where the number of species of 

 palms is given as 11,000 ! The treatment of 

 the remaining groups (Farinosse, Liliiflorse, 

 Scitaminese and Microspermse) is in all es- 

 sentials in accordance with that in Engler's 

 ' Syllabus.' 



The final chapter is devoted to a general 

 review and to suggestions of affinities between 

 the groups. This has not been well wrought 

 out, and the student will be much confused by 

 some of the statements. For example, while 

 we are told that ' the Glumiflorse represent a 

 primitive type,' and ' we may regard them as 

 the stock from which the higher series have 

 been derived,' we are told over and over again 

 that the grasses are highly specialized. The 

 diagram at the close of the chapter, while 

 helpful in enabling us to understand the au- 

 thor's position, will scarcely help the student 

 to an understanding of nature. According to 

 it there are three monocotyledonous phyla, viz., 

 (1) Helobiese, (2) Pandanales, Spadiciflorae, 

 (3) Glumiflorse, Farinosse, Liliiflorse, Scit- 

 aminese, Microspermse. 



Throughout the book, ' order ' of Engier is 

 given as ' series,' and ' family ' as ' order,' in 

 deference to time-honored English usage. 

 Here again we prefer the German practise. 



The book will be useful, and while it has 

 defects, it is the result of much painstak- 

 ing work, and must prove helpful to other 

 workers. 



Charles E. Bessey. 



The University of Nebb.^ska. 



DISCUSSION AND CORRESPONDENCE. 



CURRENTS OF THE NORTH PACIFIC. 



To THE Editor of Science: I read with in- 

 terest Dr. Bishop's letter on the source of the 

 Paciflc Coast current, and the hypothesis he 

 proposes to account for it, in Science^ of 

 September 9. 



The writer, like many others who have 

 touched on ocean currents, does not make 

 clear the distinction between the general sys- 

 tem of oceanic circulation and ocean currents 

 strictly so called. 



The former is influenced by the rotation of 

 the earth, differences of specific gravity and 

 temperature in the oceanic mass, tides, the 

 jjressure of the atmosphere and various minor 

 causes. The movement of Antarctic water 

 northward in the Pacific belongs in this cate- 

 gory, and we have no observations on record 

 which would lead us to believe that the move- 

 ment is other than very slow and gradual, or 

 that it has any marked effect in producing the 

 superficial streams of rapidly moving water 

 which we call currents. 



Oceanic currents are produced by the winds, 

 by atmospheric pressure, and by the tides, 

 modified by the presence of bodies of land. 

 Permanent currents are due almost wholly to 

 friction of permanent currents of air like the 

 trade winds. 



Dr. Bishop is quite right in supposing that 

 tlie Kuro Siwo, like the Gulf Stream, does 

 not extend across the ocean in which it orig- 

 inates. Nevertheless, the water of both, but 

 especially of the Gulf Stream, has been traced 

 thousands of miles beyond the point where 

 the stream, as a current, has disappeared. It 

 has been carried by the prevalent winds aided 

 by the oceanic circulation. 



The most complete collection of data for the 

 North Pacific together with a discussion and 

 chart may be found by Dr. Bishop in the re- 

 port of the U. S. Coast Survey for 1880, Ap- 

 pendix No. 16, published in 1882, and to which 

 little in the way of current data for the North 

 Pacific has since been added. 



The northwest trades, blowing hard and 

 steadily for ten months in the year, carry the 

 warm water, which the Kuro Siwo delivers in 

 mid-ocean, to the northwest coast, which it 



