Jan. 15, 1 8 74 J 



NA TURE 



203 



Indian Snakes 



I HAVE just had the opportunity of examining the cobra 

 mentioned in my letter dated I2th inst., togelherwith a very 

 handsome one belonging to another snake charmer. This latter 

 cobra also devoured a frog in the space of a minute or two after 

 it was placed in the basket, the frog croaking audibly about half 

 a minute after it was swallowed. 



I append the description of these cobras for the benefit of 

 those interested in such matters. 



Kiija Iripiidiaiis. — Specimen A. — Colour above very pale olive 

 with pair of conspicuous white, black-edged spectacles. A pair 

 of black fl-shaped marks on 12th, 13th, and 14th series (trans- 

 verse) corresponding to spectacles. Posterior edges of hood 

 above, dark olive. Blackish band 17th to 21st ventral and 

 corresponding scales — rest of belly mottled with dark spots. 



Lower anterior temporal in contact with three (3) other 

 temporals. 



Ventrals 1S2, sub-caudals 51, scales 23 series. 



.Specimen B, — Colour above, olive brown, with numerous 

 pale olive irregular transverse bands and blotches. Belly 

 mottled and barred with blackish. A pair of snow-white, 

 black-edged spectacles. Interstitial skin of anterior central 

 portion of hood pure white, scales pale olive ; that of posterior 

 jiortion and margins black, scales dark olive ; colour of hood 

 extending across back in strong contrast to the paler hue of 

 the body. 



A pair of white dark-edged spectacles beneath the hood, cor- 

 responding to pair above, but the white portion very much 

 wider. Central spots below oval, black, situated on loth, nth, 

 and 12th series of scales. 



Scales of head pale olive, anterior margins of vertical, supra- 

 ciliary and occipital shields dark olive, forming a double band 

 across the head. Posterior margins of occipitals dark olive. 

 A vertical infra-orbital streak of dark olive. 



Lower anterior temporal in contact with three (3) other tem- 

 porals. The following ventrals blackish, forming distinct bands 

 lyih to 31st, 24th to 30th, 35th to 3Sth, 4Sth to 51st, 6ist to 

 64th all inclusive. Beyond these there are dark bands but the 

 ventrals composing them are not as a rule black throughout. 



Ventrals 1S5, sub-caulals 53, scales 23 



Sept. 17, 1S73 E. H. Pkingle 



The use of Terms in Cryptogimic Botany 



It seems to me that there is a very perplexing want of uni- 

 formity in the names employed by different authors to indicate 

 the reproductive organs of crj'ptogamic plants. 



To a private student this want of formality in the nomenclature 

 of homologous organs is very bewildering ; especially when he 

 happens to meet with a term which no botanical work or glossary 

 within his reach explains. 



In reading the Rev. M. J. Berkeley's "Introduction to 

 Cryptogamic Botany," I have come across a term which I 

 cannot find used in the same sense in any botanical work I have 

 consulted. 



In the division of alg^ called Rhodospermere, he says, in 

 speaking of the fruit, "indefinite spores in distinct nuclei." 



In Cnllit/iamnion corymltosiim he calls the expanded wall of 

 the mother cell from whose endochrorae the walls have been 

 produced by cell division, the nucleus. 



In some other genera, he calls the cluster of naked spore- 

 Ihrtads the nucleus. In other genera the spore threads arising 

 from a placenta, together with the conceptacles containing them 

 are called a nucleus. 



In lVniii,i;i-!liaiCi! it is stated that the nucleus is composed of 

 pyriform spores arising from the endochromes of the terminal 

 cells of the spore-threads. 



I had first settled in my mind that nucleus was used by Mr. 

 Berkeley as a general name in this disvision of algce, (or an 

 indefinite cluster of spores. 



On re-consideration it seemed to me that the term nucleus in 

 the division CoigyU'SptTinea was not applied to the clusters of 

 spores, but to the expanded wall of the mother-cell, 

 or walls of the mother-cells, whose contents had been trans- 

 formed into spores ; and in the great division Desniio- 

 sfcniiCiC to the spore-threads] from whose cells the stores are 

 produced. Having at length given up this supposition 

 as untenable, it then occurred to me that "nucleus" did not 

 mean the exjianded walls of the mother-cells alone, or the 

 clusters of spores alone, or the ipore-threads alone ; but was a 



general term applied to the fruit consisting in some cases of 

 spores and spore-threads, in others spores, spore-threads and 

 conceptacles, and in others of the expanded walls of the mother- 

 cells and their contained spores. 



When, however, I again read that in Wrangelliacetie the 

 nucleus is composed of radiating pyriform spores, I gave up all 

 attempts at a solution satisfactory to myself 



Can any of your rea-lers inform me what, in this division of 

 algx, is meant by the term ' ' nucleus, " and why it is only used in 

 this division? Did the term not occur in a book written by so 

 high an authority in Cryptogamic Botany it might be passed over 

 55 a piece of affectation on the part of Uie irriter. D. E. 



POLARISATION OF LIGHT* 



in. 



XlfE now proceed to the consideration of the colours 

 ' ' produced by plates of crystal when submitted to 

 the action of polarised light. A crystal very commonly 

 used for this purpose is sclenite or sulphate of lime, 

 which is readily split and ground into flat plates of 

 almost any required thickness. If such a plate be 

 placed between the polariser and analyser when 

 crossed, it will be found that there are two positions at 

 right angles to each other, in which, if the selenite 

 be placed, the field will remain dark as before. The 

 selenite is, in fact, a doubly refracting crystal, and the 

 positions in question are those in which the plane of 

 vibration of the ordinary ray coincides with that of the 

 polariser (or analyser), and that of the extraordinary ray 

 with that of the analyser (or polariser). In every other 

 position of the selenite, and notably when it has turned 

 through 45" from either of the positions before luentioned, 

 or neutral positions as they may be called, light passes 

 through, and the field becomes bright. If the thickness 

 of the selenite be considerable, the field when bright will 

 be colourless ; but if it be inconsiderable, say not more 

 than three millimetres, the field will be brilliantly coloured 

 with tints depending upon the thickness of the plate. 



Supposing however that, the selenite remaining fixed, 

 the analyser be turned round, we shall find that in the 

 first place the colour gradually fades as before ; until 

 when the analyser has been turned through 45°, all trace 

 of colour is lost. A'ter this, colour again begins to 

 appear ; not however the original tint, but its comple- 

 mentary ; and in fact, there is no more sure way of pro- 

 ducing colours complementary to one another than that 

 here used. A general explanation of this change of colour 

 is already furnished by our former experiments. Doubly 

 refracting crystals generally, in the same way as Iceland 

 spar, divide every ray, and consequently every beam of 

 light which passes through them, into two, so that of 

 every object seen through them, or projected through it 

 on to a screen, two images are produced. These two, 

 being parts of one and the same beam of light, would, if 

 recombined, reproduce the original beam ; and the same 

 is, of course, the case with the two images. This may be 

 rendered visible by using the double-image prism as an 

 analyser, and throwing both images on the screen 

 together. As the pri^m is turned round, it will be seen 

 that, just as when no selenite was in'.crposed, the images 

 are alternately distinguished ; but that when both are 

 visible, their colours are complementary. And if the 

 distance of the prism be so adjusted that the images 

 overlap, it will be found that, when both are visible, the 

 part where they overlap is alwajs white, whatever be the 

 thickness of the plate used. 



An instructive exp-'rimerkt may be made by interposing 

 an opaque object in the path of the beam of light, so that 

 its shadow may fall upon frhe part of the field common to 

 the two images. The shadow will of course intercept the 

 hght forming each of the imciges, and will consequently 

 appear double. Suppose that the two images are 



* Continued fvom p. i6p. 



