September 1, 1897.] 



KNOWLEDGE. 



201 



I^LLUSTRATED MAGAZINE 



JTERAT 



9^ 



LONDON: SEPTEMBER 1, 1897. 



CONTENTS. 



PiOE 



201 



" Nitragin. " Bt C. F. Town-send, F.C.S 



Fairy Flies. Br Fbed. Enock, F.L.S., F.E.S. (Plate) ... 202 

 More about Antivenene. Bv Dr. J. Gr. McPhebson, 



F.R.S.fi. ". 205 



Pit-Vipers. By Lionel Jeetis 206 



The Edge of a Continent. By G-eenville A. J. Cole, 



il.R.I.A., F.G.S. {Illustrated) 208 



Letters :— J. H. S. Moxlet ; TV". Aifred Paeb ; F. 

 Whitteeox ; Edwaed Sseloeove ; W. Ltox Beowne, 

 Jim.; p. M. Rttes 210 



Science Notes 213 



Notices of Books 21-1 



Shoet Notices 215 



Books Keceived 216 



Kinetography : the Production of " Living Pictures." 



By H. Snowdex Waed, F.R.P.S. 216 



Photograph of the Nebula Herschel V 14 Cygni. 



By IsiAC RoBEETS, D.Sc, F.R.S. [riate) 21S 



Astronomical Photography.— II. The Conditions which 

 Determine the Limiting Time of Exposure. By 

 F. L. 0. Wadswoeth .". 218 



The Birds of Oban's Isles. By Haeet F. 'Witheebt. 



{Illustrated) 221 



The Face of the Sky for September. By Herbeet 



Sadlee, F.R.A.S 223 



Chess Column. By C. D. Looock, B.A.Oion 223 



"NITRAGIN." 



By C. F. TowNSEND, F.C.S. 



THE extent to which even the larger animala are 

 dependent on insignificant creatures that can only 

 be distinguished under the high powers of the 

 microscope is hard to realize. The longer we live 

 the more we find out that many of these tiny 

 organisms, far from being the harmful parasites they were 

 once thought to be, are absolutely essential to the lives of 

 their hosts. In our own blood are numerous small animals, 

 called white corpuscles, that resemble in everything but 

 size the animals known as Amiebce that live in pond water. 

 These white corpuscles, except that they cannot get out of 

 our blood or live anywhere else, are as independent as we are. 

 In diseases the destructive bacteria do not seem to be able 

 to work alone in many cases, but require the assistance of 

 other bacteria to prepare the ground for them, as it were. 

 One of the most remarkable instances of this mutual 

 dependence between higher and lower orders of beings lies 

 in the vegetable world, and is concerned with the way 

 certain families of plants obtain a portion of their food. 

 The existence of the organisms that play a part in this 

 particular co-operative arrangement is perhaps the most 

 important discovery that has been made for many years, 

 and should be of immense interest to agricultiirists and 

 others — all others. 



For a long time botanists have been puzzled by the 

 outgrowths or nodules that occur on the rootlets of plants 

 belonging to the bean and pea family. Another curious 

 thing about these plants is that to grow a crop of peas, 

 beans, or tares, is as good for the land as a strong dose 

 of manure, and many farmers, especially on the Continent, 

 have adopted the routine of growing such a crop previous 

 to sowing the land with wheat or other grain. The benefit 

 obtained by doing so was obvious, although the reason 

 was not known. Within the last few years it has been 

 found that leguminous plants (peas, beans, etc.) had the 

 power of making use of the free nitrogen of the air, and 

 that the nodules on the rootlets were the channels through 

 which the nitrogen was secured. Further investigation 

 brought to light a very complicated and interesting state 

 of affairs in these rootlets. In a thimbleful of soil there 

 are many millions of tiny organisms, with which the root- 

 hairs of the plant come into close contact. These 

 organisms — or, rather, some of them — invade the sub- 

 stance of the root-hairs and stimulate the tissues to form 

 overgrown cells, which make up the nodules we have 

 spoken of above. As fast as the cells are formed they are 

 occupied by quantities of organisms, which do not injure 

 the cells, but seem to stimulate them to intense action. 

 The result of all this is that, in a manner we do not yet 

 understand, nitrogen is absorbed from the air in considerable 

 amount. When the plant finds in the soil sufficient nitro- 

 genous food (nitrates, ammonium sulphate, or farmyard 

 manure) to supply its needs, the nodules, although they 

 are still formed, do not take nitrogen from the air, so that 

 the organisms must have some other business besides 

 supplying the plant with nitrogen. 



By cultivation in gelatine and selection, it has been 

 found possible to isolate the particular organisms that 

 take part in this curious root growth. It is found that each 

 plant has its own organism, and in the interesting lecture 

 of Dr. J. A. Voelcker, at the Society of Chemical 

 Industry, a short while since, illustrations and micro-photo- 

 graphs of these organisms were shown. Red and white 

 clover and other trifoliums patronize eight different 

 forms, although it is possible that these only represent 

 different stages in the growth of the same organism, the 

 final shape being a three-pointed star. The form peculiar 

 to the broad bean is very similar to the last, but two of 

 the arms are branched again. The vetch prefers a smaller 

 organism than the two preceding ; the shape is similar, 

 but all three arms are branched at the ends. The form 

 peculiar to broom is that of a well-formed comma, that 

 of gorse resembles a badly formed comma, and the 

 organism of lucerne reminds us of a note of exclamation. 



Our German friends, with their usual energy and 

 acuteness in matters scientific, have actually begun to 

 cultivate these organisms, and the great chemical firm of 

 Meister, Lucius, & Briining are offering them for sale 

 commercially. They have chosen for them the unfortunate 

 name of " nitragin," which is certain to be confused 

 with " nitrogen " in this country. lu Germany it does not 

 matter, as their name for nitrogen is " stickstoff." 

 Varieties suitable for the common pea and field pea ; for 

 vetches and horse beans ; for white, yellow, and blue 

 lupines ; for red, white, and crimson clover, alsike, trefoil, 

 cow-grass, and lucerne ; for sainfoin, and many others, are 

 cultivated. 



A large number of experiments were carried out with 

 these matei-ials in England last year, and Dr. Voelcker 

 gives an interesting summary of the results in his paper. 

 Unfortunately the season was so abnormally dry that the 

 experiments were not very conclusive, but the results on 

 the whole were favourable. On the land of Mr. Howard 



