48o 



KNOWLEDGE & SCIENTIFIC NEWS. 



[July, 1906. 



b(-ing- eaten by animals; tlii» wius eflccted by simulating in 

 appearance the pebbles aniong>t which they grow. 



Mciembryanthcminn triiiualinii grows amongst rolled, 

 waler-worn pebbles, which it so closely resembles in form, 

 colour, and mottling of the surface, that it is very dilVicult 

 to distinguish between the two. 



Mesembryanflinmum bolusii is even more difficult to detect 

 in its natural surroundings. The mimicry is with angular 

 rock-fragments instead of water-worn pebbles. The plant 

 consists practically of two fleshy leaves of a dull grey -green 

 colour, and the resemblance is enhanced by minute pustular 

 spots, witli which the surface of the leaves is studded. 

 1 he general effect produced is that of a lichen {Lecanoraj 

 growmg on weathered stones. This plant is rendered con- 

 spicuous for a short period by its bright yellow llowers. 



In a third plant, A nacampseros payyt-acca, also a native of. 

 the Karru, the leaves are minute, and are concealed by 

 their large, dry, membranous stipules. The general ap- 

 pearance of the plant is compared to the dejecta of some 

 bird, the branches becoming whitened towards the tips. 

 In tliis instance, the llowers are very minute, and concealed 

 under the stipules. 



New Rubber Producing Plants. 



In a f'arlianK-nt.ir) Iveporl of a l^otanical Mission 

 through the forest districts of Buddu and the Western and 

 Nile Provinces of the Uganda Protectorate, Mr. M. T. 

 IJawe announces the discovery of a considerable number 

 of forest trees, many of which are of considerable economic 

 importance. One of the most important results of the 

 mission was the discovery that the Lagos silk rubber tree, 

 Fantumia elastica, was a native of Uganda. During 

 previous years considerable expense had been incurred in 

 mlroduciiig this tree for the purpose of forming experi- 

 mental plantations. This lack of information in the present 

 instance has a compensating advantage, as, had its presence 

 been known to the natives, it would probably soon have 

 been ( xterminated, judging from the reckless manner in 

 which they collect rubber from other trees. 



Two more trees, present in abundance in various dis- 

 tricts, Landolphia dawei, and Clitandra orientalis, will, in 

 the near future, form important sources of Uganda rubber. 



Numerous Icinds of forest trees, many of gigantic propor- 

 tions, were observed during the journey, a good percentage 

 of which proved to be new to science. As examples : — 



Bahamocitrus, the type of a new genus, has large 

 globose fruits, and the seeds are embedded in a very fragrant 

 balsam. Caiiarium Schwciiifurthii is a large tree with an 

 edible fruit containing a quantity of fragrant balsam, used 

 as a substitute for incense in some Catholic churches. 



rviicedanum fraxiiiifolium, a large, umbelliferous shrub, 

 forms a favourite food of elephants. 



Jiakiiutes wihoniana, another tree hitherto unknown, has 

 a large fruit, enclosing a seed full of oil. Elephants are 

 very fond of the fruit, and are mainly responsible for its 

 distribution throughout the forest. 



Finally, a large toad-stool, common in some districts, 

 furnished with a tapering stem two to three feet long, 

 which penetrates the soft humus of the forest, is used as an 

 article of food by the natives. This also proved to be 

 undescribed, and has been named Collyhia matrorhiza. 



Arctic Flora. 



Mr. H. G. Simmons lias contributed an interesting ac- 

 count of the higher plants inhabiting the polar region, in 

 Fidenskabs-Sehkahet of Kristiania. EUesmereland, the 

 northernmost great island of the Arctic-.\merican Archi- 

 pelago, was the portion investigated, and up to the present 

 has furnished 115 species, belonging to 24 families. The 

 genera containing the largest number of species are Carcx 

 and Saxifraga (11 each); liaimncuhts (6); Draba and Foa 

 (S) ; Pedicularis, Potcidilla, and Olyceria (4 each). Of these, 

 only two genera, Androsacc and Chrysosjylcnium, and the 

 toUowing species, Alsinc llussii, Carcx mcmhiaiwpacta, 

 Taraxacum pumilum, and Fua evaijans, are absent from 

 Greenland. Of the EUesmereland flora, 72 species are cir- 

 t unipolar plants, spread all over the Arctic region, and also 

 to some extent, outside. 



Ill tropical and temperate regions, it is well known that 

 altitude is a factor of primary imi)ortance in determining 



the distribution of plants. In Arctic regions, this fact does 

 not hold good. The author states that height is of very 

 little consequence, perhaps none at all in these regions. 

 -At an elevation of a thousand feet the same species, under 

 favourable conditions, were cjuite as large and vigorous as 

 when growing at the sea level. 



Ths two important factors arc water supply during the 

 period of growth, and exposure. Southern slopes, with 

 the requisite amount of water, always furnished the greatest 

 variety and abundance of vegetation. 



CHEMICAL. 



By C. AiNswoRTH Mitciii:ll, 1;..\. tO.xon.), F.I.C. 



The Effect of Blows on Chemical 

 Elements. 



It was noticed by Herr Doermer that when metallic calcium 

 was hammered on an anvil there was frequently a fairly 

 violent explosion, accompanied by a Hash of light and 

 sparks, and it was found that the explosibility was promoted 

 by the presence of rust on the anvil, or by traces of iron 

 oxide as impurities in the metal. Professor Cohen 

 suggested that the explosion might be due to the calcium 

 having absorbed gases, just, as is well known, platinum 

 can do, and experiments showed that calcium was able to 

 occlude a considerable amount of hydrogen. The more 

 extensive observations independently made by Dr. Ohmann, 

 and recently published in the Benchte of the German Chemi- 

 cal Society, suggest that in some cases, at all events, the 

 explosion of calcium is due to a vaporisation of the metal 

 near the edge, where the pressure is greatest, and a com- 

 bination of the vapour with the atmospheric oxygen. If 

 the calcium be hammered in o.xygen the Hash produced is 

 much more brilliant, while if the metal be struck with a 

 rounded hammer only a faint light is observed, for then 

 there is less vaporisation at the edges. When several slight 

 blows are given in succession there is an accumulation of 

 heat, and eventually a gentle blow may then cause an ex- 

 plosion. Similar phenomena occur in the case of other 

 metals. Sodium hammered on an anvil gives out a bright 

 flash, and small yellow flames are sometimes produced. 

 Potassium gives marked effects with almost every stroke 

 of the hammer, small violet flames with clouds of strong- 

 smelling vapours being formed, while small incandescent 

 fragments may be split off by sharp blows. Lithium also 

 gives brilliant Hashes, frequently accompanied by a report 

 and by sparks. The light emitted is much more intense 

 than in the case of potassium. Powdered aluminium and 

 magnesium only give small sparks, and do not explode. Of 

 the non-metallic elements tried by Dr. Ohmann only phos- 

 phorus gave a positive result. It was expected that the 

 blow would cause the phosphorus to ignite, but instead of 

 this it was flattened out into a dough-like mass and emitted 

 sparks. 



Liquid Nitrogen. 



Dr. H. Erdmann has recently investigated the properties 

 of liquid nitrogen more fully than had previously been done. 

 It is a clear, mobile, colourless liquid which differs greatly 

 from liquid air in its physical properties. It produces a 

 much greater lowering of temperature on evaporation, and 

 is thus a good cooling agent. When it is poured over a 

 bulb of oxygen the gas condenses in bluish drops on the 

 inside of the glass. Liquid nitrogen is a good solvent for 

 liquids that boil at a low temperature. It mixes readily 

 with liquid ozone. As a chemical agent it is as indifferent 

 as gaseous nitrogen, and burning magnesium wire plunged 

 into it is immediately extinguished. V\"hen poured over 

 metallic calcium, however, it enters into combination to 

 form calcium nitride, which yields ammonia on treatment 

 with water. 



The Dangers of Tinned Meat. 



The exposure of disgusting practices in connection with 

 tinned meat has naturally frightened many a consumer, 

 although under proper supervision this method of preserving 



