Nov, II, 1875] 



JNATURE 



25 



rent kinds, and it is necessary carefully to distinguish 

 between them. Thus certain periodic movements occur 

 only during the growth of the part, and cease entirely 

 when the structure has become full-grown ; and the term 

 '• nutation " is restricted by Pfeffer to these recurrent 

 movements during growth. In other cases periodic move- 

 ments occur which are not determined by the growth of the 

 part, but are due exclusively to the elongation and contrac- 

 tion of certain portions of tissue ; and these latter are called 

 by Pfeffer " movements of variation." These movements 

 of variation which occur so commonly in the Leguminosae 

 are due to the action of more or less joint or hinge- 

 like portions of the leaf. Nutations on the other hand 

 which occur in very many leaves or petioles are due to 

 unequal growth of the tissues, and not to the presence of 

 a joint. As the movements of nutation are dependent on 

 the growth of the part, they cease when growth ceases ; 

 and as the zone of maximum growth of the part changes 

 its position, so also the seat of the nutation will vary. 

 The movements of variation have a very different cha- 

 racter, as they continue when the leaf is full-grown, and 

 naturally, as they depend on a definite structure having a 

 fixed position, they do not change their place during 

 growth. The two forms of movement are very closely 

 related, and jointed parts during growth often exhibit 

 movements of nutation, thus showing the close relation- 

 ship that exists between the two. 



Periodic movements, whether movements of nutation 

 or of variation, are either entirely independent of external 

 stimuli, or are conditioned by them. The former class 

 are the " autonomous " or " spontaneous " movements, the 

 latter are the " paratonic " or " induced " movements — 

 ** Receptionsbeweguu^en," and depend on the paratonic 

 action of external agents, as, for example, light and heat. 

 As a consequence of the paratonic action, the leaf makes, 

 in addition to the simple to-and-fro pendulum-like move- 

 ment, certain further oscillations with decreasing ampli- 

 tude, which Pfeffer calls " Nachwirkungsbewegungen," but 

 which for want of any better word we may call simply 

 secondary movements. It is by the help of these " secon- 

 dary " movements that Pfeffer explains the peculiarities of 

 the daily periodic movements of plants. The first chapter 

 of the work now before us is devoted to these general 

 remarks on the movements. 



The second chapter treats of the mechanism of the 

 induced movements evoked by alternation in illumina- 

 tion, the so-called sleeping and waking of plants. These 

 movements are either movements of variation, as in the 

 Phaseolus vulgaris, or they are movements of nutation, 

 as seen in the leaves oi Impatiens iwli-me-tajigere and the 

 flowers of Leojitodon hastilis. The measurements of the 

 movements are made by an instrument described and 

 figured by Pfeffer as the Lever Dynamometer. 



The third chapter treats of the daily periodic move- 

 ments. The subsequent chapters treat of such subjects 

 as the mechanism of the daily movements, the intensity 

 and internal causes of the movements, the influence of 

 temperature and gravity, autonomous movements, and the 

 like. A short chapter is devoted to the distribution of 

 periodic movements. From it we learn that movements 

 of variation are common in plants belonging to the Legu- 

 minosae and Oxalidaceae. All the plants of an order do not 

 necessarily show movements of variation. Thus in the 

 Euphorbiaceae they occur in Phyllanthus ; while in Eu- 

 phorbia we have movements of nutation. A short his- 

 torical review and resume of results concludes this most 

 interesting volume. W. R. M'Nab. 



y ahresbericht der Meteorologischen Centralstation Carls- 

 ruJie ilber die Ergebnisse der an den Meteorologischen 

 Stationen des Grossherzogthums Baden ini Jahre, 1874, 

 an^estellten Beobac/itungen. (Bearbeitet von Oscar 

 Ruppell.) 

 This report gives a very satisfactory discussion, by 

 copious tables and accompanying remarks, of the meteoro- 



logical observations made at sixteen stations in the Grand 

 Duchy of Baden during 1874. In addition to the tables 

 usually printed in such reports, the temperature is given for 

 the five-day means at all the stations. The monthly means 

 of temperature, humidity, pressure, &c., include also the 

 means of the separate hours of observation, — a feature of 

 the report which deserves, from the important practical 

 questions it throws light upon, to be more generally fol- 

 lowed. The tabulation of thunderstorms shows each day 

 on which these phenomena occurred at each of the stations. 

 This method is greatly to be preferred to giving only the 

 gross number for the separate months, since the data so 

 published \vill be available in determining the periodicity 

 of thunderstorms through the year, — an inquiry with 

 which many interesting inquiries are intimately bound up. 

 It is unnecessary to remark that 16 stations are miserably 

 inadequate as a representation of the rainfall over the 

 diversified surface of the Grand Duchy. Future reports 

 will doubtless show a large increase to the staff of rain- 

 observers. The daily pressure is given for two stations, 

 Carlsruhe (404 ft.), and Hdchenschwand (3,322 ft.), but un- 

 fortunately only the mean of the three daily observations 

 is given, instead of one, or, better still, the whole three 

 observations, it being only observations at particiilar 

 hours which can be turned to account in charting the 

 weather. 



LETTERS TO THE EDITOR 



[ 77ie Editor does not hold himself responsible for opinions expressed 

 by his correspondents. Neither can he undertake to return, 

 or to correspond with the writers of, rejected manuscripts. 

 No notice is taken of anonymous communications.^ 



Dr. Richardson's Hygeia 



The eloquent address in which Dr. Richardson has sketched 

 the possible Health City of the future might furnish matter 

 for much discussion — among other points, the probable statistics 

 of the commimity. The author contemplates the possible re- 

 duction of the death-rate to 8 per 1,000 in the first generation, 

 and to 5 or less in the next, as suggested by Mr. Chadwick. It 

 sounds simple enough to talk of knocking i or 3 per 1,000 from 

 a death-rate, and, so long as the rate is tolerably high, such as 

 20 or more, the effect is not so startling, but when we come to 

 such low figures as 8 and 5 the difference becomes enormous. 

 Thus, whereas a diminution from 21 to 20 raises the expectation 

 of life by only 1 4 years, a fall from 9 to 8 raises it by 9, from 

 6 to 5 by 21 years, and from 5 to 4 by 40 years. We should 

 thus have at 8 per 1,000 death-rate an expectation of life of 86 

 years, and probable mean duration of 120, whilst there would 

 be cases of old people living to 160. Again, at 5 per 1,000 the 

 ages would be respectively 137 years for expectation at birth, 

 and old people living on to 250 ; at 4 per 1,000 the expecta- 

 tion would be 177, and old people would hve to beyond 330. 

 Compare these figures with Dr. Richardson's closing address, 

 where he claims a modest 90 years as the proper length of 

 human life. 



Another aspect of the case is the probable increase of popu- 

 lation, which we may thus calculate : — The mean birth-rate of 

 England for the last 35 years is 33*8 ; if the death-rate be 5 the 

 net increase would be 28 8 per 1,000. At this rate the popula- 

 tion of Great Britain and Ireland would reach 66,000,000 by 

 the year 1900, and, by the year 2000, no less than 1,120,000,000, 

 or about the present population of the inhabited globe. At the 

 same time the model City of HygeLa would more than double 

 itself by the end of the present century, whilst, by the end of 

 the next, its population would be 3,450,000, or as nearly as 

 possible that of our overgrown metropolis. What check does 

 Dr. Richardson contemplate to this inordinate hypertrophy ? 



F. DE Chaumont 



Photography in the "Challenger" 



When the Challenger was fitted out, I was asked to prepare 

 certain special drj' photographic plates to go with her. I wished 

 to give them the sensitiveness of wet collodion and unhmited 

 keeping qualities, and the following letter from the chief photo- 

 grapher on board is very satisfactory. The stains alluded to en 



