January i6, 19 13] 



NATURE 



543 



normal soils, but we do find abundant evidence of the 

 activity of organisms detrimental to the ammonia- 

 producing- bacteria. We are therefore justified in re- 

 garding these detrimental organisms as one of the 

 factors limiting soil fertility. We have shown that 

 partial sterilisation destroys these organisms, and that 

 it causes an increase in numbers of ammonia-produc- 

 ing bacteria, in the amount of ammonia produced, 

 and in the lertility of the soil ; these factors are all so 

 closely connected with one another that no reasonable 

 doubt" can be entertained of the existence of a causal 

 relationship between them. E. J. Russell. 



I-iothamsted Experimental Station, Harpenden. 



Precocity of Spring Flowers. 



I HAD occasion to remark in a letter to Nature 

 (No. 1477, vol. Ivii., p'ebruary 17, 1S98J on the 

 imusually early flowering of many winter and spring 

 flowers in the December of 1S97 and the January of 

 1S98; so many of these records have been surpassed 

 already during the recent remarkably mild period that 

 I am venturing to put a few of them before your 

 readers. For the last twenty years I have kept a 

 record of the first flowers of about eighty species of 

 wild and garden spring flowers in this county, and 

 the season named above is the only example which 

 at all approaches the present one in the precocity of 

 flowering. 



The winter aconite began on December 8, and has 

 been flowering profusely since the middle of the 

 month, when about a hundred blossoms were gathered 

 in one day; other early dates are December 20, ign, 

 December' 23, 1897 ; the first week in January is the 

 mean, the latest January 27, 18S7. Green hellebore, 

 January 10; usually end of February; latest, March 

 26, 1902. Fetid hellebore, December i ; usually early 

 February; latest, February 21, 1904. Lesser celan- 

 dine, December i ; usually early February ; latest, 

 March 12, 1900; other early records, January 20, 

 189S and igoi. W'ild white sweet violet in the 

 hedges, January 5, many to be seen now, whereas 

 mid-February to early March is its usual season. 

 Pyrus japonica on many walls has been as much 

 covered with flowers throughout December as it is 

 usually in April and May. 



Strawberry-leafed cinquefoil, December 24 ; usually 

 begins in February. Gooseberry, January 5 ; a bush 

 in the garden with many opened flowers. Hedge 

 parsley abundant in the hedges in January ; usually 

 begins in mid-April. Louicera fragrantissima, from 

 December 18 onwards ; usually begins early in 

 January ; earliest, December 10, 1900. 



Adoxa moschatdlitia (Moschatel), in bud January 

 11; usually flowers in April. Petasites jragrans 

 (winter heliotrope), mid-November, occasionally as 

 early, but more usually December and January. 

 Yellow coltsfoot, January 7 ; usually early March ; 

 earliest previously, January 21, 1898, February 20, 

 1897 ; latest, March 26, igog. Primroses abundant in 

 December and early January. Omphalodes verna 

 abundant December ; usually early March ; latest, 

 April I, igo2. Spurge laurel, December 20; usually 

 early in February; January 12, igi2, January 29, 

 1898, March 18, 1897. Dog's mercury, d flowers, 

 November 28; earliest previously, December 21, 1900; 

 latest, March 12, igoo. Hazel, both d and 9, 

 January 5; earliest d, December 24, 191 1, 9, January 

 16, igo6. 



Chimonanthiis fragrans (winter sweet), very 

 abundant from November 14 ; earliest before, Decem- 

 ber 9, 1907. Yellow crocus, January 5 ; earliest, 

 January 22, igoi, January 24, 1898. Galaiithus 



NO. 2255, VOL. go] 



Elwesii, November 14. Common snowdrop, Decem- 

 ber 28; earliest, January 8, igi2. Foliage has been out 

 for some time on honeysuckle and elder, and even 

 the "brushwood sheaf round the elm-tree bole is in 

 tiny leaf," which, according to Browning, should not 

 occur until April ! Flower-buds are swelling on 

 English elm and grey willow. 



Eleoxora Armitage. 

 Dadnor, Herefordshire, January 13. 



Many references are being made to the numbers of 

 plants in flower now to be found in various parts of 

 the country. May I give a list of those I gathered 

 on January 6 in our garden in South Devon, ranging 

 from 230 to 500 ft. above sea-level? 



Gorse (double French and single), ivy, jasmine 

 (yellow), honeysuckle, crocus (yellow), polyanthus, 

 primrose, berberis, Daphne mezereuni, ribes (pink and 

 white), daisy, veronica (purple and pink), laurustinus, 

 azalea (white), rhododendron (red), clianthus (" par- 

 rot's bill ") mignonette, heath (white and Mediter- 

 ranean), violet (Russian, white, and Neapolitan), rose 

 (pink, yellow, and " Dorothy Perkins "), genista 

 (yellow), passion-flower, forget-me-not, snowdrop, 

 lavender, cyclamen, tobacco-plant (white), ivy gera- 

 nium (pink), wallflower, borage, Helliborus (foetidus, 

 orieiitalis, and niger), arabis, Garrya eUiptica, arbutus, 

 solanum, pansy, Aubrietia purpurea, and Pieris 

 (Andromeda) floribunda. T. Mary Lockyer. 



Salcombe Regis, Sidmouth. 



The effect of the mildness of the winter is shown 

 in the number of wild plants now in flower, some of 

 them evidently survivors from the autumn, others 

 early spring flowers, and )'et others entirely out of 

 season. During a walk on January 3 and 4 from 

 Brighton through Ditchling and Haywards Heath to 

 Balcombe, we observed no fewer than thirty wild 

 flowers in blossom, many of them being abundant. 



The list is as follows: — Daisy, gorse, dandelion, 

 cinquefoil, primrose, feverfew, avens, red deadnettle, 

 hawkweed, groundsel, chickweed, shepherd's purse, 

 yarrow,, lesser celandine, garlic mustard, dwarf 

 spurge, spear thistle, barren strawberry, ivy-leafed 

 speedwell, corn marigold, dog's mercury, dove's-foot 

 crane's-bill, field speedwell, herb robert, white dead- 

 nettle, cress, lesser periwinkle (a garden escape), and 

 the following, all young plants : wild-beaked parsley, 

 buttercup, and rose campion. 



Edith How Martyn. 



Light Perception and Colour Perception. 



The Departmental Committee on Sight Tests has 

 recommended a method of classifying colour-blindness 

 by measuring the luminosity of the colour sensations 

 by means of the flicker method of photometry. The 

 degree of abnormality is estimated by the ratio of 

 red to green compared with the normal. This classi- 

 fication is absolutely erroneous. Light perception and 

 colour perception are quite distinct — that is to say, 

 there may be considerable defect of colour perception 

 without defect of light perception. The first two cases 

 of colour-blindness (dichromics who confused red and 

 green) examined by me on the method suggested by 

 the Committee had a ratio identical with the normal, 

 whilst a man who had not the least defect of colour 

 perception had an abnormal ratio. Prof. A. W. Porter 

 and I examined one of the above-mentioned colour- 

 blind men bv another method, and we could not detect 

 the least defect in the perception of luminosity in any 



