278 



NA TURE 



[August 26, 1922 



Rudbeckia and Aquilegia. 



When recently (July) collecting Eocene fossils in 

 the vicinity of Roan creek, Colorado, I saw for the 

 first time the singular composite Rudbeckia montana 

 Gray in life. It abounds in the valleys and gulches, 

 occupying similar positions to those in which one 

 finds R. lacimata on the eastern side of the range. 

 The latter, so far as I could ascertain, is absent from 

 the region of R. montana, though it occurs in the 

 south-western part of Colorado. The striking feature 

 of R. montana is the total absence of rays. The 

 large conical or cylindrical discs appear very black, 

 slightly yellow from pollen when in flower. The 

 involucral bracts are coarse and pointed, surrounding 

 the base of the disc and diverging at various angles. 

 The whole effect is most peculiar and unusual. Ray- 

 less Compositae are known in various genera, and 

 occasionally occur as mutations in normally rayed 

 genera. The ancestor of R. montana was presumably 

 rayed, but losing its rays through a germinal modi- 

 fication, how did it manage to survive and flourish 

 to the exclusion of the rayed form ? 



On July 21 I took particular occasion to watch a 

 large group of R. montana on Dry creek, a tributary 

 of Roan creek. The plants appeared just as attract- 

 ive to bees as the rayed species. 

 They were being visited by great 

 numbers of worker Bombus, the 

 majority B. rufocinctus pliacelia: 

 Ckll., but there were also many B. 

 edwardsii bijarius Cresson. Other 

 bees were fewer, but I collected 

 females of Megachile pugnata, sav, 

 M. grindeliarum Ckll. and Halictus 

 trizonatus Cresson. There were 

 also two species of plant-bugs, 

 Lygceus reclivattts, say, and Lygus 

 pratensis L. Thus it seems certain 

 that the loss of the rays has not 

 interfered at all with cross-pollina- 

 tion by bees. 

 |j On the high mesa, between Roan 

 creek and Salt Wash, in the aspen 

 groves, I first saw the white-flowered 

 sub-species of the Columbine, Aquilegia ccerulea James. 

 The large white flowers, with long spurs (up to 90 

 mm.), dotted among the green shrubbery, were 

 truly magnificent. One got the impression of a 

 perfectly distinct species ; but some of the flowers 

 were suffused with bluish, and rarelv one found a 

 genuine A. ccerulea with blue, sepals. The flowers 

 certainly averaged larger than those of ctzrulea, but 

 the spurs were long enough for Tidestrom's pinetorum, 

 which seems possibly to be a habitat-form. 



The locality on the Roan mountains is in the midst 

 of a Canadian zone flora, with no pines, the only 

 conifer being Pseudotsuga mucronata, which is abun- 

 dant. Pinus edulis and Sabina occur on the slopes 

 lower down. The underlying geological formation is 

 the Green river Eocene. The white (albiflora Gray) 

 sub-species of A. ccerulea may well have arisen by 

 mutation from the blue-sepalled type, but how did 

 it manage to supplant it ? It cannot be a matter 

 of the direct effects of the environment since genuine 

 ccerulea grows rarely in the same localities. Both 

 forms are visited by Lepidoptera, and there is no 

 reason for supposing that ccerulea is specially favoured 

 by butterflies, albiflora by moths. In the locality 

 of albiflora, as we found it, long-tongued moths must 

 be very rare, but long-tongued butterflies (especially 

 Papilio) abound. 



These cases of Rudbeckia and Aquilegia are difficult 

 to explain. Is it possible that, while there is no 

 direct influence of the]_environment on the characters, 



NO. 2756, VOL. I IO] 



r IG. I. — Ra<if\ ikia ! 

 tana t ( Iray. \ nat 



there is something in the soil (the shales being rich 

 in peculiar organic products) which has affected the 

 germ-plasm of the plants, bringing about a selective 

 elimination of certain qualities ? 



T. D. A. COCKERELL. 



University of Colorado, Boulder, 

 July 25. 



The Rat and its Repression. 



Tin: valuable contributions on rat repression by 

 Lord Aberconway and Lieut. Alfred E. Moore, which 

 have appeared in the columns of Nature, may, I 

 venture to think, be usefully amplified by some 

 reference to one of Britain's paramount industries : 

 shipping, considered in the light of the rat menace. 



Undoubtedly, rats represent a serious problem to 

 the shipping industry, and I only suggest some 

 possibilities that occur to me in the hope that others 

 more competent may be induced to table something 

 more valuable. Among the avenues to be explored 

 are : — 



(a) The possibility of an international agreement 

 in regard to ship fumigation and disinfection, having 

 special regard to ships arriving at British Empire 

 ports. 



(b) The possibility of stimulating invention in re- 

 gard to ship-proofing : e.g. anchor chains, mooring 

 ropes, gangways, and all shore connexions are avenues 

 of infinite possibility when one is considering rat 

 invasion. 



(c) The possibility of stimulating research into the 

 most effective means of destroying rats aboard ship 

 by means of fumigation, electricity traps, raticides, 

 etc. 



(</) The possibility of creating a national board 

 composed of the representatives of port authorities, 

 ship owners, authorities on rat repression, and ship 

 store superintendents, and of providing in connexion 

 with such national maritime board suitable labora- 

 tories for testing and research. 



(() The possibilities of asbestos - concrete plus 

 barium carbonate as a light and at the same time 

 poisonous covering in the place of wood where its 

 use would not be inconvenient. 



It is doubtful if man has a more cunning foe than 

 the rat, and in view of the fact that the vermin is 

 ever increasing, and the rat's adaptability when it 

 is called upon to vanquish obstacles to its depreda- 

 tions, it seems to me well worth our while to con- 

 centrate upon effective measures to counter the 

 activities of our enemv. Denbigh. 



The Bath Club, 34 Dover Street, W.i, 

 August 4. 



The Spectrum of Helium in the Extreme 

 Ultra-Violet. 



Mr. Fricke showed (Phil. Mag. 41, May 1921) that 

 in the extreme ultra-violent the arc spectrum of 

 helium probably _contained but one line with a wave- 

 length near 585 A.U. 



I have recently attacked the subject again using a 

 vacuum spectroscope so arranged that a good vacuum 

 could be maintained in the body of the apparatus 

 while the discharge tube contained helium at a 

 pressure of about a millimetre. No window was 

 employed, the success of the device depending on the 

 use of a very short and narrow slit and upon the 

 suitable application of a powerful pump, 



With a continuous current the line at 584-4 is of 

 very great strength, and is accompanied by three 

 in u inns at 537-1, 522-3, and 515-7 whose intensities 

 decrea e with their wave-length and in a manner 

 strongly suggesting a series relation. Luckily the 



