742 



NATURE 



[August 12, 1920 



Bees and the Scarlet-Runner Bean. 



Darwin directed attention to the slight asymmetry 

 in the petal growth of the scarlet-runner bean, 

 Phasioliis multtflorus, that offered advantage to the 

 bee for more easily reaching the nectar on that side 

 of the flower where fertilisation would be helped by 

 the visiting insect. I remember some years ago many 

 times satisfactorily confirming the recorded fact by 

 observation, but this year 1 am surprised to note 

 quite a different practice In respect to insect visits 

 to these flowers. 



The humble-bees follow the habit they have long 

 acquired in rifling the tubular flower of the jasmine 

 of its honey : that of gnawing a hole near the base 

 of the corolla, through which the proboscis can reach 

 and extract the nectar. A similar plan is now adopted 

 with the flower of the scarlet-runner bean. The bee 

 no longer dives into the more open side of the bloom, 

 where it would brush against the protruding anthers 

 and stigma in an endeavour to reach the nectaries at 

 their base, but on alighting moves immediately to 

 underneath the blossom and, if not already done, 

 gnaws through the calyx and sheath of filaments 

 close to the nectaries, which are then easily reached 

 and emptied. The honey-bees follow, and this season 

 I have observed no instance of an insect attempting 

 to reach the honey in the way the development of 

 the flower suggests as that of reciprocal advantage. 



The asymmetry of the bloom is due to the pecu- 

 liarly coiled shape that the carina or keel part of the 

 papilionaceous corolla develops. This caUses the 

 stamens and pistil to take a spiral form as they 

 grow through and protrude together from the 

 extremity of the enveloping carina, and exposes them 

 between the more separated left wing and standard 

 petals. 



Though perfectly adapted to self-fertilisation, the 

 flower, by the change of habit of the bees, would 

 appear to lose the occasional advantage of cross- 

 pollination, and the injury done bv the gnawing of 

 the bloom apparently causes a diminution in the 

 amount of pollen formed and a quicker fading and 

 falling of the bloom, with the probable consequence 

 of fewer pods "setting." Harford J. Lowe. 



The Museum, Torquay. 



The Condition of Kent's Cavern. 



Since a recent visit to Kent's Cavern I have been 

 wondering if it would be possible for something to 

 be done by which anv important finds that may be 

 made there could be brought to the notice of those 

 interested in ancient man. The cave now seems to 

 be one of the sights of Torquay which any curious 

 visitor can see, just as he visits the caves elsewhere 

 when on a holiday. There is a well-informed man 

 who shows the sights to visitors, and he stated to a 

 party, of which I was one, that quite recently a jav^- 

 of a human being had been found, and that this was 

 in the possession of a local collector. A human tooth 

 has also been found. It seems highly desirable that 

 the jiaw should be e.xamined by a competent authority. 

 During the famous excavations which were made 

 some years since a jaw was found, but this was 

 examined and described only a year or two ago ; and 

 although Prof. Keith thought that it represented the 

 Neanderthal type in this country, I believe Dr. Duck- 

 worth pronounced that it did not differ from modern 

 races. If this further jaw were examined the question 

 might be settled, and it would be of great interest 

 if it were found that, after all, the race was actually 

 represented in this country. 



Edward A. Martin. 



285 Holmesdale Road, South Norwood, S.E.25, 

 July 29. 



NO. 2650, VOL. 105] 



Calculation of Vapour Densities. 



When determining vapour densities I believe that 

 many, if not most, experimenters go through three 

 processes, viz. : (i) Correct the observed volume to 

 that at N.T.P. ; (2) find the mass of hydrogen which 

 would ^occupy this latter volume ; and (3) divide this 

 mass of hydrogen into that of the substance used, 

 whence density d on the hydrogen standard is found. 



Now if we evaluate the constant R in the gas equa- 

 tion pv — RT, using mm. of mercur3-column as units 

 of pressure p, and taking v as the gram-molecule in 

 litres — which on the oxygen sta/iidard at N.T.P. is 

 224 litres — we get the figure 62-36. 



Then, for finding density, the equation becomes 



where m is the mass in grams and v is in litres. 



To quote an example : 05 gram of iodine e.xpelled 

 50 c.c. of air at 17° C. and 750 mm. from V. Meyer's 

 apparatus. Was the temperature to which the iodine 

 had been subjected high enough to cause dissociation? 



This problem, if done by the "three processes," 

 takes some time, and gives d= 119-6, which now 

 requires to be multiplied by 1-008 if we wish to com- 

 pare it with published figures for atomic weights 

 (iig-6x 1-008=120-56). 



Losing the single equation given above, 

 ^^_ o-5X 62-36 X29o _^^p 

 2x750x005 



The answer to the problem is evident. Slight dis- 

 sociation had occurred, since d for L demands 126-9 



I venture on these remarks because R is seldom, if 

 ever, given in the above-mentioned units. It is ex- 

 pressed usually in such units as are suitable for 

 solving energy problems. This number, 62-36, is an 

 "equator" of the four steps which themselves, no 

 doubt, are valuable from an educational point of view. 

 Readers of N.\ture who are engaged in science teach- 

 ing may find the "equator " of some service. 



Reginald G. Durrant. 



Rosetree, Marlborough, July 31. 



Use of Sumner Lines in Navigation. 



Capt. Tizard's reference to m\- book entitled "The 

 Sumner Line," etc. (Nature, July i, vol. cv., p. 552), 

 contains an error which should be corrected. His 

 statement regarding what he calls the zenith point, 

 " which spot is named by Mr. Comstock the sub- 

 polar point," seems to imply that I have introduced 

 a new name not approved in the criticism that 

 follows. In fact, I have nowhere used the obnoxious 

 term "sub-polar point," but have employed in this 

 connection a well-known phrase, " the sub-solar 

 point," for which I can claim no authorship. See 

 Young, "General Astronomy," 1898 edition; ^luir, 

 "Navigation," 1918, et al. G. C. Comstock. 



Washburn Observatory, L'niversity of Wis- 

 consin, Madison, July 20. 



I regret that I inadvertently wrote "sub-polar " for 

 "sub-solar" in my remarks on Prof. G. C. Com- 

 stock's book on Sumner lines, but this lapse makes 

 no difference really to the statement that the proper 

 description should be zenith point, and not sub-solar 

 point (see p. vi of preface and pp. 2, 3, 5, etc.). 

 Sub-solar refers to the sun only, and does not neces- 

 sarily include sub-stellar or sub-lunar, but zenith point 

 is common to all. T. H. Tizard. 



23 Geneva Road, Kingston-on-Thames, 

 August 5. 



