March 26, 1903] 



NA TURE 



501 



features of the germination, infection and growth of the 

 mycelium of the Uredo in the tissue of grasses. Primarily, 

 the figures refer especially to the Uredo of Puccinia dispersa 

 in the tissues of Bronius sccalinus, but comparisons are 

 made with the behaviour of this and other Uredinea: — e.g. 

 Puccinia glumarum and P. graminis — in the tissues of other 

 grasses and cereals. 



The research, which has been carried on for more than a 

 year and a half, and has involved the preparation and micro- 

 scopic examination of thousands of sections, is principally 

 based on the application of improved hardening and staining 

 methods to preparations from tube cultures of the grasses 

 concerned, the leave:; of which were infected at definite 

 spots. These tube cultures wsre prepared according to the 

 method previously described.' At definite intervals after 

 sowing the spores — e.g. after one, two, to six and eight days 

 — the infected areas were removed and placed in fixing 

 solutions, and the life-history of the fungus traced step by 

 step, and controlled by reference to uninfected areas. 



The full paper is illustrated by numerous figures, and deals 

 with the behaviour of the nuclei, vacuoles, septa, branches, 

 haustoria, and other details of the hyphoe up to the com- 

 mencement of spore-formation. 



The relations of the hyphae and haustoria to the cell- 

 contents of the host are critically examined, and the cumu- 

 lative evidence not only fails to support Eriksson's " Myco- 

 plasm " hypothesis, but is completely subversive of it, so far 

 as histological facts are concerned. 



Eriksson's hypothesis, which refers the epidemic out- 

 breaks of rust to the sudden transformation into the mycelial 

 form of a supposed infective substance, previously latent 

 and invisible in the cytoplasm of the host, is shown to be 

 untenable because the corpuscules specianx of this author 

 are proved to be the cut-off haustoria of the fungus. 



Eriksson supposes that these corpuscules (haustoria) are 

 formed by the hitherto latent germs in the host-cells, grow- 

 ing up in the cells into vesicles, which then pierce the cell 

 walls and give rise to hypha; in the intercellular spaces. 



The present paper shows that Eriksson has entirely re- 

 versed the true order of events. The haustoria have been 

 formed by the hyphae, and figures are given showing every 

 stage in their development. The first haustorium may be 

 formed by the infecting tube immediately after its penetra- 

 tion through the stoma, and figures are given showing the 

 remains of the germ-tube outside a stoma, the swelling of 

 its tip over the stoma into an appressorium, the passage 

 through the stomatal cavity, and its development into a 

 vesicular swelling whence the true infection tube arises, 

 which latter may at once put forth a haustorium. In some 

 cases all these latter phenomena are visible in one and the 

 same preparation. 



The author expresses his thanks to Miss E. Dale, of 

 Girton College, for valuable aid during the later stages of 

 the work, in the embedding and cutting of numerous 

 sections. 



" The CEstrous Cycle and the Formation of the Corpus 

 Luteum in the Sheep." By Francis H. A. Marshall. 

 Communicated by Prof. J. C. Ewart, F.R.S. 



Physical Society, March 13.— Dr. R. T. Glazebrook, 

 F.R.S., president, in the chair. — A paper by Dr. Farr, on 

 the interpretation of Milne seismograms, was read by Dr. 

 Chree. Prof. Milne and Dr. Omori have come to the con- 

 clusion that the tilts represented by the maximum displace- 

 ment of the boom of a horizontal pendulum seismograph 

 are too large to be admissible as true tilts. The author has 

 investigated the motion of the boom analytically, and his 

 results show: (1) that the boom does not vibrate with its 

 own natural period, but takes the frequency of the disturbing 

 force : (2) that the friction should be small compared with 

 the difference of the squares of the frequencies ; and (3) that 

 the phenomenon of beats may occur between the forced 

 vibration and the free period of the boom. The maximum 

 amplitude of swing of the boom gives no information what- 

 ever of the amplitude of the disturbing cause without also 

 a knowledge of the periods of the forced and free vibrations. 

 The author shows how to determine the amplitude of the 

 wave by observations on these quantities. The author has 



1 "On Pure Cultures of a Uredine, Puccinia distersa (Erikss.) " (Roy 

 Sac. Proc, 1902, vol. lxix. p. 461). 



NO. 1743, VOL 67] 



verified the results of his analysis by experiments with 

 artificial waves of known periods produced by an apparatus 

 described in the paper. In conclusion, it appears (1) that 

 strict attention should be paid to recording accurately the 

 period of free vibration of the boom ; (2) that the tape should 

 be driven at such a speed as to enable the period of forced 

 vibration to be determined ; (3) that the effect of friction 

 should be recorded. — A potentiometer for thermocouple 

 measurements was exhibited and described by Dr. Lehfeldt. 

 To make a satisfactory potentiometer for thermoelectric 

 work, it is essential that it shall not introduce a high re- 

 sistance in the circuit of the couple and galvanometer. 

 Most of the potentiometers on the market, well enough for 

 comparing voltaic cells, fail in this respect. Dr. Lehfeldt 

 has therefore designed an instrument specially suited for 

 thermocouple work. — Dr. J. A. Marker exhibited and de- 

 scribed a direct-reading potentiometer for thermoelectric 

 work. The instrument represents a form which has been 

 designed and made in the National Physical Laboratory. 

 Dr. Harker has experienced similar difficulties to Dr. Leh- 

 feldt, and the instrument which he has designed is similar 

 in many respects to the one exhibited by him. — A paper on 

 the measurement of small resistances was read by Mr. A. 

 Campbell. The object of this paper is to give a brief 

 account of a number of measurements of a set of low re- 

 sistance standards belonging to the National Physical 

 Laboratory. The tests were made partly with a view to 

 comparing various methods of measurement. The re- 

 sistances were of manganin, and their nominal values were 

 approximately o'i, 001, o'ooi international ohms. The 

 following methods were employed : — (1) Shunt potentio- 

 meter; (2) Kelvin bridge; (3) two-step bridge; (4) differ- 

 ential galvanometer ; (5) Matthiessen's and Hockin's method. 

 The last method was found to be much less accurate than 

 the other four. The results obtained from the other methods 

 are tabulated in the paper, and show very satisfactory agree- 

 ment. — Dr. R. A. Lehfeldt read a paper on a resistance 

 comparator. Objecting to sliding-contacts on account of 

 the thermoelectric effects they tend to introduce; and irregu- 

 larities slide-wires show when a good deal used, the author 

 has substituted for the slide-wire two coils of 99 ohms each 

 connected by twenty coils of o'i ohm each. The latter are 

 arranged circularly, so that a switch connected to th' 

 galvanometer may be set on any one of the intervening 

 studs. The galvanometer deflections are taken for tire two 

 positions nearest balance and interpolation to 1/100 calcu- 

 lated. In this way an accuracy of one part in 100,000 is 

 attainable. The author thinks there is a gain of accuracy 

 as well as of convenience in using the interpolation method. 



Royal Astronomical Society, March 13. — Prof. H. H. 

 Turner, president, in the chair. — The secretary read a letter 

 from Mr. S. C. Chandler directing attention to a new 

 term in the variation of latitude that had been discovered 

 by Mr. Kimura, of the International Latitude Station in 

 Japan. Mr. Chandler had been unable to find anv probable 

 explanation for the term, and proposed that, for its investi- 

 gation, a southern belt of latitude stations should be estab- 

 lished, suggesting stations at Sydney, the Cape of Good 

 Hope and Santiago de Chile. — Mr. Newall read a paper 

 on observations made at Cambridge of the velocitv in the 

 line of sight of certain selected stars, his communication 

 being the first instalment of a work undertaken in accord- 

 ance with a scheme of cooperation. — A paper by Dr. Max 

 Wolf on three of Sir W. Herschel's observed nebulous 

 regions in Orion was read, illustrated by a photograph, in- 

 cluding three of the regions described by Sir W. Herschel 

 as nebulous, but in which Dr. Isaac Roberts's photographs 

 had shown no nebulosity. Dr. Wolf's photographs, on the 

 contrary, showed considerable nebulosities. Dr. Roberts 

 criticised Dr. Wolf's results, and read a communication of 

 his own on photographs of various nebulae, including ten 

 which are new. — Mr. Whittaker gave an account of a com- 

 munication from Prof. Simon Newcomb on the desirability 

 of a reinvestigation of the problems arising from the mean 

 motion of the moon. Prof. Newcomb called attention to 

 the discrepancies between the predicted and observed places 

 of the moon, and showed the comparative failure of attempts 

 hitherto made to explain them. He considered it necessary 

 to reinvestigate the whole question ab initio, and suggested 

 a thorough comparison of the tabular and observed places 



