170 



NA TURE 



\yuly 2, 1874 



guide the bee's proboscis to the apertures in the staminal 

 tube, which it is to be remembered are on each side of the 

 central tenth stamen ? Mr. F. Darwin has suggested a 

 function of this kind for a somewhat similar structure on 

 the free tenth stamen of Phaseolus. 



C. nionlana is a small plant, very like C.glaucam struc- 

 ture. The flower forms compact umbels ; the claws of 

 the petals are short, with a wide opening above the calyx ; 

 the tenth stamen is free, but the staminal tube is close- 

 fitting, and there is no nectar inside the flower. Pc'r 

 contra, there are distinct glands or bubbles of liquid on 

 the outside of the calyx, which is much infested by aphis. 



C. minima is similar in structure ; and both these 

 species or varieties are similar to C. glai(ca. 



We have then in this genus a number of species or 

 varieties, all of which have their tenth stamen free, but 

 which differ widely in other respects. 



1. In C. emcrus and C. cmerus hitcscens the nectar is in 

 the base of the staminal tube, and is accessible by the 

 separation of the tenth stamen in the usual manner. 



2. In C. varia, C. montana, C. giauca, and C. minima 

 the staminal tube is barren of nectar, but the nectar is 

 secreted outside the calyx, and the access to it is provided 

 for by a special gap between the petals. 



In both cases, however, the flower is so constructed 

 that the bee in getting the nectar which he wants dusts 

 himself with and carries from flower to flower the pollen. 



Sonic questions remain. The separation of the tenth 

 stamen and the gap between the petals and the separate 

 stamen both exist in all the species ; where one is of use 

 the other is useless. Wliy do they co-exist ? Did one 

 exist before the other ? and is one of them now useless 

 and rudimentary ? If so which was the earlier and which 

 the later in development ? 



A further observation arises. These Coronillas are 

 foreign plants, and in many gardens and greenhouses 

 have only been introduced recently. In my own garden 

 in Surrey I have introduced C. varia and C. emerus from 

 London within these last four years, and I am not aware 

 of any other plants in the neighbourhood. But the bees 

 seem quite to understand how to get the nectar from 

 both. In C. emenis this is not surprising, for there are 

 many other common flowers — Robinia, Pisum, Vicia, 

 Lalhyrus, &c. — similarly constructed. But I know of no 

 flower common in England which is like C. varia in 

 having the neclar outside the calyx, with the peculiar 

 access to it through a gap in the petals. And yet the 

 Surrey bee found his way to it at once. Does not this 

 look as if the bcc had sufficient intelligence to adapt his 

 doings to a perfectly new and unknown structure ? 



T. H. Farrer 



LEAZ'S DOCTRINE OF OCEAN CIRCULATION 



AVERY elaborate memoir was presented to the Royal 

 Society at its last meeting, by Mr. Prestvvich, con- 

 taining a digest of all the observations made upon deep- 

 sea temperatures previously to the Lightr.iitg cruise of 

 1868, which was the starting-point of all those recent re- 

 searches that have excited so strong and general an 

 interest. Of these obssrvations, some of the most impor- 

 tant were quite unknown to the scientific men of the 

 present day, until brought to light by Mr. Prestwich's 

 patient research ; and I would take the earliest oppor- 

 tunity of particularly calling attention to those of Emil. 

 Lcnz', an eminent German physicist, formerly settled in 

 St. Petersburg,* who accompanied Kotzebue in his second 

 Circumnavigation Voyage in 1823-26. Of this voyage, the 

 obtaining of deep-sea temperatures was one of the special 



* The list of Lenz's papers occupies four columns of the Royal Society's 

 Catalogue. A large proportion of them consist of original researches, both 

 experimental and mathematical, in electric'ty and magnetism. And I am 

 assured by Sir Charles VVhealstone th.at these are of the highest merit, and 

 were greatly esteemed by Gauss arad Jacobi, the two great masters in this 

 department of investigation. 



objects ; and, with a view to accuracy of observation, 



experiments were previously instituted by Parrot upon the 

 influence of pressure on self-registering thermometers, of 

 the same kind as those made by Mr. Casella under the 

 late Prof. W. A. Miller and myself in 1869. And the 

 St. Petersburg professors satisfied themselves by their 

 experiments (as wc did by ours nearly fifty years later), 

 that any observations taken by sending down ordinary 

 thermometers to great depths must be seriously vitiated 

 by the pressure of the superincumbent water. 



Instead of attempting, however, to improve his thermo- 

 meters by the protecting outer bulb -'' which made our 

 instruments thoroughly trustworthy, Lcnz devised a method 

 of obtaining deep-sea temperatures, which must have 

 been very difficult to work, and which required a good 

 deal of mathematical computation to bring out its results ; 

 yet this in his able hands gave temperatures which prove 

 to be in close accordance with the thcrmometric observa- 

 tions of the Chalhngcy. He also made throughout the 

 voyage a careful series of observations on the temperature 

 of the ocean at the surface and at moderate depths below it, 

 which proved to be of the greatest value in the establish- 

 ment of his general doctrine. And he further made an 

 important series of observations on the salinity of ocean- 

 water as indicated by its specific gravity. The increase 

 of the density of sea-water with the reduction of its tem- 

 perature down to the freezing-point, was known to Lenz 

 through the experiments of Dr. Marcet in this country, 

 and of Erman in St. Petersburg ; and he was conse- 

 quently free from the influence of the "dominant idea" 

 that the deep water of the ocean, like that of the Swiss 

 lakes, would have the uniform temperature (39?.° F.) of 

 fresh water at its greatest density ; which obviously in- 

 fluenced the conclusions subsequently drawn from their 

 own observations by D'Urville and Sir James Ross, and 

 led to the general adoption of those conclusions. 



The whole series of these observations, with the mathe- 

 matical computations required for the determination of 

 the real bottom-temperatures, are contained in a most 

 elaborate memoir, entitled " Physikalische Eeobach- 

 tungen, angestellt auf einer Reisc um die Welt, untcr 

 dem Commando des Capitains von Kotzebue, in den 

 Jahren 1823-26," presented to the St. Petersburg Academy 

 miS29,and published in vol. i. of its "Transactions" (1S31). 

 No one can examine this memoir without being impressed 

 with the remarkable abiUty it displays ; a peculiarly com- 

 petent judge, Prof. Debus, whose attention I have directed 

 to it, assures me that it is a model of admirable physico- 

 mathematical investigation. 



It was not until 1S45, however, that Lenz gave forth the 

 general conclusions to which he was led by his own ob- 

 servations and those of others (so far as known to him) 

 in his admirable " Bemerkungcn iiber dicTemperatur des 

 Weltmeeres in verschiedenen Tiefen," published in the 

 "Bulletin" of the St. Petersburg Academy for 1847. He 

 there shows that his own conclusions as to the low tem- 

 peratures obtained at great depths are not invalidated by 

 the observations of others, indicative of higher tempera- 

 tures taken with ordinary thermometers; but may still be 

 taken as indicating the presence of glacial water on the 

 bottom of each of the great oceans, even under the 

 equator. And from a discussion of the numerous tempe- 

 rature-observations taken at the surface and at small 

 depths beneath it, Lenz deduces the important conclusion 

 iJiat there is at a}id under the equator a belt of water 

 cooler than the luater to the north anU south of it. Of 

 this striking phenomenon, he says, the explanation flows 

 directly from the form of the isothermal curve which re- 

 presents it ; and this explanation I shall presently repro- 

 duce in his own terms, which will be found singularly 

 accordant with those used by myself in the notice I 



* It is right to rcaall the fact that this "protection" was lirst devised 

 by Admiral Jb'itzroy, and was practically worked out by Messrs. Negretti 

 and Zambra, as far back as 1857. 



