April 16, 1903 



NATURE 



57i 



the equator until they terminate in latitude +8o°. The 

 general trend of the spots is from latitude ±35° to +5°. 



(3) At epochs of prominence minima (which are con- 

 current with sunspot minima) these centres of action are 



SUNSPCTS" 1 



MEAN O.1.-1 



AREA '* 



N HEM' 



1 LAT3 



MINI) jj 



ME6 N ;(h 



-EtlOCRfc^MIC 

 LATITUDE OF I 



SUNSPOTS' 



SORTH 0*" 



EQUATOR & 



80 

 LATlTUCt 

 or bO 



?HOMiNENCES 



N HEM' 4 ° 



{RICCO -20 



MASCAftl) 0- 



80- 

 LATITUDE 



" 60 



PROMINENCES 



40 



-20 

 (TACCHINt) 

 0- 



LATITU0E 

 of -20- 



?R0MINENCES 

 40 

 S HEM' 



60 

 (TACCHINI) 



BO- 

 OT 

 LATITUDE 



" -20 

 'R0MINENCES 



SHEfV* 

 (RICCO 60 



B 



lASCARl) 



80 



MEAN Q 



HCLlOGRAPm: 

 L.ATITUDC OF 



SUNSPOTS 10 



EQUATOP t-V 



?00MlNCNCE'J 

 nrBtOOENCILS . 

 SOUTH LATS 

 ( TUCCMlNll 



SUNSPOTS^* 



"CAN DAILY 



AREA «& 

 SHEM' 



D 



syfvc 



these cut curves C when two zones of spots are in evidence, 

 and intersect the curves A and B when there are only single 

 zones of prominences. 



(4) At nearly all other times these centres are apparent 

 in two zones, while those of the spots 

 19000 occupy only one in each hemisphere. 



This deduction is true if the curve-; C 

 be taken as representing simply the 

 phenomenon generally, but it should be 

 borne in mind, as stated previously, that 

 a new reduction of these spot zones, 

 which is in hand, is necessary. 



(51 The subsidiary maxima exhibited 

 by the curves representing the percent- 

 age frequency of prominence activity 

 for each entire hemisphere are due to 

 the presence of two well-developed 

 centres of prominence activity in each 

 hemisphere. 



To make the comparison the sub- 

 sidiary peaks on the curves D should 

 be compared with the curves A and B, 

 and in every case the former are accom- 

 panied by two zones of prominences. 



Before concluding this article it may 

 be mentioned that other observers, and 

 among them Father A. Fenyi, S.J., 

 have studied this question of promin- 

 ence distribution, but their discussions 

 have been restricted to only compara- 

 tively short intervals of a few years ; 

 their results are, however, in harmony 

 with those described here. 



It is important finally to state that the 

 deductions here made may be partially 

 incomplete owing to the difficulty of 

 determining sometimes whether a new 

 centre of action has been formed or the 

 position of an old one changed. Further, 

 account must be taken of the fact that 

 the material discussed does not repre- 

 sent the record of the percentage fre- 

 quency of prominences determined from 

 observations made on the disc of the 

 sun (now rendered possible by the 

 Jannsen-Hale-Deslandres method), but 

 one obtained from observations of the 

 phenomena occurring only at the limb 

 of the sun. The close agreement be- 

 tween the observations of the different 

 observers shows nevertheless that this 

 latter method is of great value. 



William J. S. Lockyer. 



18700 



I88OO 



I890O 



Fig. 2. — A comparison of curves illustrating the variations of the positions the cenlres ol 

 action of prominences (a and b) and spots (c), the percentage frequency of prominences (p), 

 and the variation of spotted area (e). (The continuous and broken vertical lines indicate 

 the epochs of sunspot maxima and minima respectively, the two hemispheres being laken 

 together.) 



restricted to one zone (about latitude ±44°) in each hemi- 

 sphere, while those of the spots occupy two zones in each 

 hemisphere. 



Since the broken vertical lines in Fig. 2 represent the 

 epochs of prominence and spot minima, it will be seen that 



ISO. 1746, VOL. 67] 



THE STATOLITH THEORY 

 OF GEOTROP1SM. 1 



THE paper deals with the modern 

 theory 2 of the mechanism by which 

 plants are enabled to regulate their line 

 of growth bv means of the force of 

 gravity. When an upright flower-stalk 

 is forcibly subjected to a change of posi- 

 tion, for instance by laying the flower- 

 pot on its side, it responds by geotropic 

 curvature, and finally regains the 

 vertical. The statolith theory is not 

 concerned with the mechanism of curva- 

 ture, but merely with the question how 

 horizontality can originate a stimulus, 

 in other words, how the plant perceives 

 that it is no longer vertical. It is 

 known that in some animals, for ex- 

 ample the Crustacean Palsemon, the 

 faculty of spacial orientation depends 

 on statoliths (otoliths) which serve as 

 guides by pressure on the internal 

 surface of the otocyst. This theory has now been applied 



1 A paper by Mr. Francis Darwin, read at the Royal Society, March r2. 



- Published simultaneously by Haberlandt and Nemec in vol. xviii. of the 

 Berichte d. Deutschen Bot. Gesell. ; see also Pringslieim's fakrb-, rols. 

 xxxvi., xxxviii. 



I900O 



