March 31, 1898] 



NATURE 



5»» 



point must, therefore, be guarded first ; and we see that 

 nature has done it by closing the window with one of the petals 

 of the inner whorl. This petal is convex in front and concave 

 behind, while the hood is convex behind and concave in front. 

 This arrangement shuts off the window completely (Fig. 3). 

 The petaloid shutter is secured in its place, on either side, by 

 the margins of the hood to nearly an eighth of an inch. These 

 margins are very much thinned out, and are also cemented 

 together. The shutter, being on the concave side of the bud, 

 comes in contact with the convex bract beneath, which thus 

 helps to keep it in position. The top of the hood is closed 

 similarly air-tight by its margins. The inner whorl — i.e. the 

 corolla — is represented usually by the shutter alone. Some- 

 times, however, two petals are present, and very rarely all the 

 three. 



The male organs, thus tightly packed, can neither move from 

 their place, nor can they be assailed by any foreign element 

 from without. 



(2) Arrangement of the stamens. — On removing the hood and 

 the shutter we come to the androecium, which consists of four 

 or five stamens. The filaments are petaloid and erect, thus 

 -embracing the pistil completely. The anthers are adnate or 

 ■dorsifixed. They are also introrse, i.e. turned towards the 

 stigma. . 



Let us now proceed to the pistil, and examine it in the 

 different stages of its growth. In the early state — i.e. before 

 it is ripe, and before the anthers are ripe also — the style and 



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but I subsequently found that it had been invented previously 

 by Lieut. -Colonel Moessard under the name of monocular 

 stereoscope {Cosmos, May 23, 1896). 



In this stereoscope one eye views one of the pictures directly, 

 while the other eye sees the other picture after reflection at two 

 mirrors, the angle between whose planes can be adjusted so as to 

 bring the image into apparent coincidence with the picture seen 

 by the first eye. In viewing distant pictures, such as lantern 

 slides, a projecting partition, with a flange whose breadth is 

 nearly equal to the distance between the two eyes, is all that is 

 necessary to prevent either eye from seeing the wrong picture. 



For lantern work, either two pictures could be projected side 

 by side with separate lanterns, or two small views could be 

 photographed side by side on the same slide, and thus enable 

 stereoscopic effects to be shown with a single ordinary lantern. 



Moreover, by turning the arrangement of mirrors through 90° 

 it can be made to displace the image seen by one eye vertically 

 instead of horizontally. This would enable the two pictures of 

 an oblong view to be projected one above the other, instead of 

 side by side, and viewed with the same apparatus as before, but 

 differently arranged. As regards the foreshortening of the 

 upper picture, this would be to a great extent compensated for 

 by the fact that the lantern itself projected the picture upwards. 



It is evident that two pairs of mirrors, one for each eye, could 

 be used if desirable. G. H. Bryan. 



the stigma project beyond the androecium. If this state con- 

 tinued, self- fertilisation would be impossible. The stamens 

 must either overtake the stigma, or the stigma must be at the 

 tnercy of insects or the wind for pollination. The stamens are 

 not quick enough in growth to overtake the stigma ; so what 

 happens is this. By the time the anthers are ripe, the style 

 shortens in length by bending nearly at right angles in two 

 places {often marked by horizontal grooves in early stages), 

 and thus brings the stigma in contact with the pollen (see 

 Figs. 4 and 5). After pollination is completed, the style 

 straightens again and projects, as before, beyond the androe- 

 •cium (see Fig. 6). Stages intermediate between Figs. 4 and 5, 

 may be seen if we examine the flowers from without inwards. 

 With the straightening of the style, the anthers become free and 

 curve outwards. The bracts fall off ; the shutter drops away ; 

 the hood withers, and the style dries gradually. 



Kolhapur, India, February 17. Go pal R. Tambe. 



Stereoscopic Projection of Lantern Slides. 



In your report of the meeting of the Physical Society on 

 February 26 (Nature, p. 454), I notice an account of the 

 ■exhibition, by Prof. T. C. Porter, of a somewhat complicated 

 apparatus for exhibiting lantern slides in stereoscopic relief. 

 An equally elaborate arrangement, depending on the use of 

 polarised light, was exhibited at the British Association at 

 Nottingham in 1893. It may possibly, therefore, be of interest 

 to call attention to the much simpler means of acconiplishing 

 the same result, which suggested itself to me some time ago, 



NO. 1483. VOL. 57] 



The Aurora of March 15. 



I was fortunate enough to witness the display of the aurora 

 on the night of the I5ih, and think that some of the appearances 

 may be of interest to those who did not see them, but who have 

 recorded the accompanying magnetic disturbances. 



The display began in the north-east about eight o'clock, by 

 the appearance of a brilliant band of light, rising from behind a 

 cloud 45° from the horizon, and extending about 30° in a south- 

 westerly direction. This band might have been mistaken for a 

 search-light, the edges were so sharp. The colour was the 

 characteristic greenish hue of the aurora. 



Alter persisting steadily for five minutes the band gradually 

 broadened and shortened, and became a bright patch, which 

 continued until the end. The display spread over the northern 

 sky to the west, where another patch appeared. At nine o'clock 

 the display was very fine, with two patches east and west, and 

 right overhead seemed to be the apex of a parabola with beams 

 of light streaming northwards. Looking southwards, occasional 

 flashes of a yellowish pink colour could be seen. About ten 

 o'clock the whole energy of the display seemed to become con- 

 centrated in the east and west patches, and great flashes of light 

 connecting the two. After this the brightness seemed to 

 gradually diminish. 



So bright was the aurora at its height that the grey granite 

 walls of the houses were illumined by the flashes. 



Aberdeen, March 25. A. Geo. Smith 



On Phosphorescent Sap in Superior Plants. 



In answer to the question of Prof. Giglioli in Nature of 

 March 3 (p. 412), I beg to observe that in Meyen's "System 

 der Pflanzen-Physiologie," which was certainly in its time a 

 standard work, there is to be found in vol. ii. p. 203 ( Berlin, 

 1838) a short but concise statement of the phosphorescence of 

 the milk-juice in Euphorbia phosphorea, on the authority of 

 V. Martius (" Reise in Brasilien," ii. pp. 726 and 746), as 

 also a reference to a communication by Mornay {Philosophical 

 Transactions, vol. vi. p. 279), on the phosphorescence of the 

 milk-juice " in einem rankenden Gewachse, Cipo de Cunanam 

 genannt, welches zwischen Monte Santo und dem Flusse 

 Bendego wuchs und wahrscheinlich eine Asclepiadee oder ein 

 Apocyneeist." M. W. Beijerinck. 



Delft, Holland. ^ 



A Remarkable Case of Correlation. 



A very interesting case of correlation is recorded in the 

 Bulletin of the Botanical Department, Jamaica, for December 



1897. 



Particular attention has been paid lately to the selection of 

 good Ripley pine-apples, and it is found that if there is a broad 

 red stripe in the centre of the leaf the fruit will turn out good ; 

 in other cases the fruit goes into holes at the bottom, and is 

 attacked by ants. S. N. C. 



