NA TURE 



[Dec. 31, il 



limited number and the uncertainty of the correction for change 

 of heat with phase render more certainty as to the fact desirable, 

 we may (accepting them as probable) reason thus. 



Previous observations both at Allegheny and Mount Whitney 

 have shown that the solar rays are transmitted with greater and 

 greater facility (except for cold bands) as the wave-length in- 

 creases up to the point (near \ = 3'') where they suddenly dis- 

 appear altogether. This shows either that (i) the solar heat, 

 which, according to the customary assumption, exists to an 

 unlimited wave-length before absorption, has here been cut off 

 by a suddenly absorbent action, like that of a cold band extend- 

 ing indefinitely below 3'', or (2) that, either through a precedent 

 absorption of such rays in the sun's own atmosphere or their 

 non-existence, no solar rays below 3" present themselves to our 

 atmosphere for admission. 



The first view is that which I have treated as most in accord- 

 ance with received opinion. It is not, however, the only one, 

 since the second is not to be absolutely rejected, considering 

 our experimental ignorance of the laws of radiation from 

 gaseous bodies for great wave-len^jths. Of these two liypo- 

 theses we see that, according to the first, our atmosphere is 

 quite opaque to all heat below 3', and the writer's (unpublished) 

 experiments show that heat above this point must come almost 

 wholly from a source much above 100° C. In this view, then (unless 

 we agree that the radiations from the lunar soil correspond to a 

 source much above 100° C), we conclude that sensibly none of 

 them pass our atmosphere, but that what we receive is diffused 

 and reflected heat coming within the range of the known solar 

 energy spectrum, and transmitted with nearly the same facility 

 as solar heat, or if with a little greater, because lowered in 

 wave-length by selective reflection at the lunar surface, not by 

 absorption and re-radiation from the lunar soil. 



In the second view, for anything we have absolutely known 

 to the contrary, our atmosphere may be permeable to radiations 

 of any wave-length below 3", and we could draw no certain 

 inference, even if the lunar radiation were more distinctly 

 different in transmissibility than it is. 



As a matter of fact, with the actually limited diff'erence in the 

 character of its transmissibility, a difference which, as so far 

 determined, is of the same order as that of the error of observa- 

 tion, we have no ground then from this present class of observa- 

 tion (/>. Class 3) for any absolute conclusion one way or the 

 other. But, we repeat, it seems to be a probable inference from 

 our whole work that the earth's atmosphere is more diather- 

 manous to heat of extremely low refrangibility than has hereto- 

 fore been supposed. 



(4) Co?nparative Transmission of Glass for Lunar and Solar 

 Heat. — The evidence here, which at first seems to so directly 

 support the view of a sensible radiation from the surface of the 

 moon, proves, on examination, to be subject to other interpreta- 

 tion, for the observed effect is almost certainly due in part to a 

 degradation of wave-length by selective reflection from the lunar 

 soil. 



We can draw no absolute conclusion, then, from this evidence, 

 at first in appearance so promising, though we may say that it 

 certainly indicates an increased probability for the view that 

 radiations from the lunar soil may be transmissible by our 

 atmosphere. 



(5) Observations during a Lunar Eclipse.— li our own ob- 

 servations in this respect are imperfect, those of Lord Rosse, 

 before cited, are, on the other hand, clear. They appear to 

 bear but one interpretation— that all heat from the moon dis- 

 appears immediately that it passes into the earth's shadow, and 

 there is no evidence of any being retained, for any sensible time, 

 more than if it were reflected. 



It is so difhcult to conceive that while the moon has been 

 storing heat during many days of sunshine, it can part with it 

 instantly, so that the temperature of the whole earthward surface 

 of the planet disappears in an inappreciable interval, that m jst 

 will see in this observation an argument against the existence of 

 any such heat >ensible to us at any time whatever. 



(6) Formation of a L'lnar HmI .Spectrum.— The observations 

 made here with the lunar heat spectrum are as yet incomplete. 

 With improving experience and apparatus, we hope to make 

 others which shall give information of a character no other 

 means can furnish (see note, infra). 



Coniliision.—Vih.\\e we have found abundant evidence of heat 

 from the moon, every method we have tried, or that has been 

 tried byothers, for determining the character of this heat appears 

 to us inconclusive; and, without questioning that the moon 



radiates heat earthward from its soil, we have not yet found any 

 experimental means of iliscriminating with such certainty be- 

 tween this and reflected heat that it is not open to misinterpret- 

 ation. Whether we do so or not in the future will probably 

 depend on our ability to measure by some process wliich will 

 inform us directly of the wave-lengths of the heat observed. 



Note added February, 1S85. — Since the above paragraph was 

 written, we have succeeded in obtaining measures with rock-salt 

 prisms and lenses in a lunar kcat spectrum. These difficult 

 measures must be repeated at many lunations before complete 

 results can be obtained ; but, considering their importance 

 to the present subject, we think it best to st.ite now in 

 general terms, and with the reserve due to the necessity 

 of future experiment, that they indicate two maxima in the 

 heat curve — one corresponding within the limits of errors of 

 observation to the sjlar curve maximum, the second indefinitely 

 lower down in the spectrum, corresponding to a greater amount 

 of heat at a lower temperature. Exactly what temperature this 

 latter corresponds to we have no present means of knowing. 

 We have succeeded, however, in forming a measurable heat- 

 spectrum from the surface of a Leslie cube containing boiling 

 water, and tire maximum ordinate in the lunar heat curve 

 appears to be below the maximum ordinate in the hot water 

 curve. The inference from this is, of course, that the tempera- 

 ture of the lunar soil is, at any rate, below that of boiling water, 

 and in an indefinite degree. 



We cannot close this note without calling attention to the 

 remarkable fact that we here seem to have radiations from the 

 moon of lower wave-length than from the sun, which implies an 

 apparent contradiction to the almost universally accepted belief 

 that the sun's emanations, like those from any heated solid body, 

 include all low wave-lengths representing temperatures inferior 

 to those certainly emitted. 



SYMBIOSIS BETWEEN FUNGI AND THE 

 ROOTS OF FLOWERING PLANTS 

 A VERY remarkable phenomenon has for some time past 

 ■^ attracted the attention of a few physiological botanists in 

 France and Germany, and w.as the subject of an interesting dis- 

 cussion at the annual meeting of the Association of German 

 Naturalists and Physicians at Strassburg in September last. 

 This is no less than the discovery of the fact, which may now be 

 considered fairly established, that a considerable number of 

 phanerogams, especially forest trees, do not draw their nourish- 

 ment directly from the soil, but through the medium of an in- 

 vesting layer of fungus-mycelium, to which B. Frank gives the 

 name of iVIycorhiza. 



The observations which first called the attention of botanists 

 to this interesting subject were those of F. Kamienski, on 

 Monotropa hypopitys, published in the Mem. de la Soc. Na 'ionale 

 des Sei. Nat. de Cherbourg. He came to the conclusion that 

 this plant is not, as is usually believed, a parasite, the most care- 

 ful observation failing to detect any haustoria or other parasitic 

 union with the root of any host. On the other hand, he found 

 the root of the Monotropa to be completely covered by the 

 mycelium of a fungus, which branches abundantly, and forms a 

 pseudo-parenchymatous envelope, often two or three times the 

 thickness of the epidermis, and especially well developed at the 

 apex of the root. This fungus, the species of which M. 

 Kamienski is unable to determine, is entirely superficial, not 

 penetrating into the living cells, though occasionally forcing its 

 way between those of the epidermis. He contends that the 

 Monotropa derives its nourishment from the soil entirely through 

 the medium of this fungus-mycelium ; the only parts of the root 

 which are in actual con'act with the soil are composed of lifeless 

 cells with no power of deriving nutriment from them. The con- 

 nection of the fungus with the roots of the Monotropa is not one 

 of parasiti=m, but of true symbiosis, each of the two organisms 

 deriving support and nutriment from the other. 



More recently similar observation; on the mode of nutrition of 

 treei belonging to the natural order Cupuliferie have been made 

 by Dr. B. Frank and confirmed by M. Woronin (both recorded 

 in the Berickte der Deutsch. Bot. Gesellschaft). Dr. Frank finds 

 the roots of our native oaks, beeches, hornbeams, chestnuts, 

 and hazels, to be covered by a dense cirtex of Mycorhiza, 

 organically associated in growth with the root, and composed 

 entirely of fungus-hyphx, completely enveloping the whole of 

 the root, even the growing point. The structure of this cortex 

 is that of a sclerotium ; it is composed of a dense mass of hyphae. 



