May, 1904.] 



KNOWLEDGE & SCIENTIFIC NEWS. 



91 



In other cases the same stimulus may be responded to 

 in quite a diflerent manner. When certain younf^ roots 

 are exposed to it they curve so as to place themselves in 

 the same position with regard to the incident rays, but 

 with their growing apices in the opposite direction. 

 \"arious tendrils, peduncles, and other organs respond in 

 a similar manner. Leaves tend to place themselves 

 across the incident rays. 



Among the obvious difficulties which beset the course 

 of a root in making its way through the soil is that of 

 impinging more or less directly upon some particle which 

 it is unable to displace. In practice it is nearly always 

 found to be able to grow past such an obstacle. The 

 situation affords us another example of stimulus appre- 

 ciated and responded to. Contact with the apical portion 

 of the young root causes an immediate departure from 

 the straight line of growth. The behaviour of the organ 

 can be studied on a germinating bean with great readi- 

 ness. If such a structure be kept in moist sawdust till 

 the young root emerges, then be transferred to a moist 

 chamber and suspended therein, a small piece of hard 

 substance, such as card-board, can be attached by 

 a little cement to the side of the lip. The root at once 

 begins to curve away from the side thus touched, and if 

 the stim.ulation is maintained for some time the resulting 

 growth will cause the root to grow into a loop. If a 

 tendril of Passi flora gracilis have a small loop of thread 

 laid upon a certain portion of it, it will curve at once and 

 in about two minutes will assume the form of a helix. 

 Other tendrils behave in a similar way on coming into 

 contact with different hard supports, though the rapidity 

 of their response varies considerably. 



The nature of the response must, however, be con- 

 sidered before we can associate it in any co-ordinated 

 fashion with the stimulus. Such co-ordination between 

 the two must be put in evidence if we may fairly deduce 

 such an appreciation as we can call sensation. 



The first thing that strikes an observer is the evident 

 purposeful character of the response. The position 

 assumed in relation to the incidence of the lateral light is 

 that which will ensure an equal illumination of the sur- 

 faces of all the leaves. These spread out at approxi- 

 mately equal angles with the stem in all its sides, and 

 hence w^hen the stem is parallel to the light source the 

 greatest amount of sunlight falls upon the green surfaces 

 of the plant, where the work of forming sugar under the 

 influence of such light is taking place. The opposite 

 effect produced upon roots is calculated to press them 

 closely into the soil, where their absorbing hairs can have 

 free play. The curvature of the tendril assists it to 

 secure a holding for the plant, so that its weak stem 

 escapes being trodden down and its leaves are enabled to 

 reach light and air. 



A less obvious consideration is afforded by the fact 

 that the parts of the plant receiving the stimuli are in 

 cases strictly localised. The receptive part of a root is 

 just behind its apex ; that of a young seedling stem is in 

 about the same position. Not only is this part localised, 

 but it is situated in quite a different part from that which 

 effects the movem.ent. The latter is caused by grov.-th 

 some half-inch or so nearer the base, at a part which is 

 quite insensible to stimulation. 



Another consideration which bears upon the question 

 is that an extremely small stimulus is able to bring about 

 a very considerable effect, and that there is no simple 

 ratio between the intensity of the stimulus and the extent 

 of the response. An instance of this is afforded by the 

 behaviour of the tendril of Passiflora already described. 



We can, therefore, associate stimulus and sensation and 

 point to the response of the plant as evidence of both. 



Saturn. 



.At the beginning of May Saturn rises 2i hours before the 

 sun .ind telescopic observation may be renewed, tliouf,'h the 

 planet will scarcely be far enoiif^h west of the solar orb to be 

 presented under very satisfactory conditions. The ensuing 

 apparition of this attractive object is likely to prove of great 

 interest. His southern declination will he 3' less than it was 

 last year and this ought to bring about an improvement in the 

 definition. 



In the summer of igoj Saturn displayed the evidences of 

 considerable activity in a niunber of bright and dark spots, of 

 irregular form, distrihntcd in about N. lat. 35' along the polar 

 side ofthe northern equatorial beU (" Knowleoge," Dec. iy03). 

 In June, July, and Augnst these markings were frequently 

 seen, though but few observers appear to have retained them 

 in view during the autumn mouths. The rotation period of 

 the chief spot or spots was variously determined as follows :— 

 Observer or Period. Days of We«<5rence. -^ 



Authority. li. 111. Observation. ,>> . v 



K.Graff .. 10 39 o' 3 , ^5«. >^''* 3S830t V^ V 



J. C. Sola .. 1038-4 3f-. ^5£.. JVac/i. 389ij<\\ T 



" - ■ 10 380 18' .-• ■ -Sj V V^ 



10 38-8 ' 40 ^5<.j;aj(ii\547. ^,v 



P. Fauth 

 'E. E. Barnard 



L. Brenner . . 



10 38-0 

 h. in. 



H. W. Wilson 10 38 4iS|a\>'7S!' ^'^.?^^^'; '°^ 



i^ 



•(;. W. Hough.. 

 •G.W. Hough.. 

 tW. F. Denning 



10 38 27' 

 10 38 30'5 

 10 37 56 4 



53 



24^' 



129 



l^ilIihNot. Dec, 1903. 

 Monthly Not. Dec, 1903 

 Monthly Not. Jan., 1904. 



* In these cases the identifications were uncertain and the resulting periods 

 probably excessive. 



f Mean value derived from observations of i8 spots. 



As soon as Saturn can be successfully examined it will be 

 important to ascertain whether the markings continue percep- 

 tible. Possiblv, at the present time, the northern hemisphere 

 shows nothing'more than the beautifully symmetrical belts and 

 zones which usually stripe the disc. The material of the 

 differently tinted irregularities seen in 1903, which proliably 

 resulted from extensive eruptions affecting the atmospheric 

 scenerv, may have amalgamated with the ordinary bands of 

 the planet and quite lost their distinctive outhnes. And the 

 region affected mav remain (juiescent for a time to be again 

 disturbed by further outbreaks in the near future. The phe- 

 nomena occurring on Saturn are, no doubt, very similar to 

 those visiblv taking place on Jupiter, and observation has 

 taught us that on the latter planet one disturbance scarcely 

 subsides before another forces itself into prominence. The 

 spots common to certain latitudes of Jupiter possess some 

 physical resemblances, and are characterised generally (though 

 not invariablv) by nearlv identical rates of motion, according 

 to the longitudinal current in which they are placed. The 

 same thing is likely to be displayed on Saturn, and the few 

 following years may be expected to furnish useful evidence on 

 this point. 



The spots on Saturn remained fairly conspicuous objects m 

 December, 1903, and observers will probably redetect them 

 during the present spring. If so, it will be desirable to obtain as 

 many transits as possil)le, 90 that the individual objects may 

 be satisfactorily identified and their periods of rotation rede- 

 termined. ,•,.,, r ,. 



The markings referred to certainly exhibited some of the 

 vagaries which occasionally affect the features on Jupiter, for 

 the rate of their motion underwent a decided acceleration at 

 the close of the apparition. Several of the principal objects 

 which, during the summer, gave a period of lohrs. 38 ruin. 3 sec. 

 conformed witli a shorter period of 10 hrs. 37 min. 50 sec. 

 during the latter part of the autumn. 



In regard to Saturn, the year 1903 will be remembered as 

 one of considerable historic interest, for the rotation of the north 

 temperate region was found to be 235 minutes greater than that 

 derived by Professor Hall from his equatorial spot of 1876, 

 and the fact rendered conclusive that this planet, like Jupiter, 

 displays atmospheric spots affected by large proper motions. 



Mr. Crommelin's " Ephemeris for Physical Observations of 

 Saturn. 1903-4" {Monthly Notices, December, 1903) will be 

 found extremely useful in the further study of this interesting 

 object. w. F. Den.ning. 



