Vol. 711. No. 169. 



THE AGRICULTURAL NEWS. 



331 



SCIENCE NOTES. 



The Improvement of Agricultural Plants. 



An account of the methods which are in use for 

 obtaining new varieties of agricultural plants is given 

 in an article by M. Schribaux, published in the 

 Bullefiii di' la tivcietd (V Eitcdii riiycmenf /nmr V In- 

 diistrie nafiovale for Ma^^ last. These methods fall 

 into three groups — (1) careful watch js kept for sports, 

 i.e., plants which, for no obvious reason, differ from the 

 others : (2) variation is induced by altering the condi- 

 tions of growth : (3) suitable plants are ' cro.ssed' 



The following summary of the .above-mentioned 

 paper, together with references to other jjapers bearing 

 on the same subject, and published elsewhere, appeared 

 m XdJure of September 3 last: — 



The tir-st iiietliod mentioned by which new varieties are 

 obtained is nece.s.sarily haphazard, .since .sports can obviou.sly 

 not be predicted ; it has, however, proved very useful in 

 the past, and has yielded many valuable varieties of potatos, 

 of fruit trees, etc. The second method promi.ses very 

 interesting result.?, for some plants respond quickly to 

 changes in their surroundings. J[. Schribaux sowed in 

 a garden soil the seeds of the wild carro), an annual with 

 a woody root. In two generations a certain number bad 

 become biennials, with a fleshy root like the culti\ated carrot. 

 ]M. Blaringhem adopted quite a different, method with maize. 

 Plants were cut down just as thr ear wa.s beginninsj: to 



..." o o 



develop, i.e., at the time of maximum vital activity ; 76 per 

 cent, of those surviving developed abnormally. Some were 

 permanently altered ; thus a late I'umisylvaiiia maize was 

 converted into an early variety. 



Another instance of great practical iniiiortance is 

 furnished by the grape vine. After struggling long and 

 vainly against the ravages of Phylloxera, tlie French vine- 

 growers have made up their minds to live with it. M, A'iala 

 visited America and brought back sonie vines which had 

 become .so differentiated from those growing in Fiance that 

 they withstood the attacks of the pest. Unfortunately, they 

 would not grow on calcareous soils, but became very chlorotic, 

 and further search was made. Vines were in the end 

 discovered capable of withstanding Phylloxei'a and of grow- 

 ing on calcareous .soils ; these have solved the problem for 

 tlie French grower. Perhaps the lase^of the sugar-beet is 

 most interesting. The grower requires roots containing 

 a large percentage of sugar, a low proportion of the accom- 

 panying salts, and i-ai)al)le of resisting adver.st- conditions. 



The .selection is made, in the first instance, on the basis 

 <if the sugar content. A large injnilier of roots can be 

 rejected by simple inspection, for high sugar content is 

 correlated with certain external features ; the other roots are 

 examined chemically, since it is found that removal of 

 ;t portion for this purpo.se does not interfere with subsequent 

 growth. The very best are then cut up into a number of 

 pieces to be grafted into other roots; they ]iroduce seed, 

 which is .sown, and yields roots for further selection. 

 M. Schribaux states that a single root has yielded sixty-four 

 pieces, each capable of ]iroducing seed. \' It is not surprising 

 that the percentage of sugar has gone up from 1 1 per cent. 

 in 1870 to T6 or b'< per cent, to-day. 



There is evidence, however, that the process will not go 

 on indefinitely, for roots containing more than IS percent, of 

 sugar cease to vegetate properly. Sir W. T. Thiselton-Dyer 

 discusses this asjiect of the c|ncstion in the ■/(Jiiriiii/ of the 



Board of Agrii'ultiu-e for .\pril, taking the potato as an illus- 

 tration. Like the sugar-lieet. the potato has been the subject 

 of continual .selection, and the cijd result is a highly aitificial 

 tuber of great commercial valu« but ditticult of cultivation. 

 The practical man speaks of degeneration, but Thiselton-Dyer 

 does not consider this to be the case. He jioints out that the 

 potato has been induced to hrad itself with starch far in 

 excess of any natural reijuiremefit of the plant, and suggests 

 that too much is being demanded of the plant, and the 

 machinery for the processes Of growth has reached its breaking 

 jKiint. 



■We can control nature in altering the constitution of 

 a jjlant ; but eventually a liarrier is reached beyond which it 

 is impossible to go.' 



It is often found difficul't to fix the new varieties 

 obtained by selection. Even when asexual reproduction Ls 

 possible, as in the case of trees and potato.s, the variatit)n 

 freipiently does not remain permanent, and many promising 

 vaiieties have disaiipeared. When reproduction is by seed it 

 is still more difficult to fix a variety ; this is abundantly 

 proved by the difficulty of improving wheat. A single ear 

 is selected because it possesses some desirable property ; the 

 seed from it is sown ; an ear is selected showing the same 

 jiroperty, and the process is continued for se\eral generations. 

 ' Pedigree ' seed is thus obtained, but it rarely remains true ; 

 the farmer has to renew his .stock periodically from the raiser 

 ■vvho keeps on the selection process. The work done on the 

 selection of seed wheats at the lloseworthy Agricultural 

 College is described in the .Toiinml of Aijricultiin- for South 

 Australia : it is ho|)ed in this way to obtain strains whicli 

 will keep their character for two or three seasons and prove 

 much more piofitable than the .seed wheat now in use. There 

 is no question that a good deal can be done by selection, 

 especially in South Australia where, we are told, little or no 

 attention has been given to the fuatter, and the best grain is- 

 sometimes sold and the worst kept for seed. But it is now 

 clear that the only safe method for the improvement of crops 

 grown from seed is to bieed on Mendelian lines, as Profes.sor 

 1!. H. Ritf'en is doing at Cambridge, and South Australia 

 would do well to breed, as well as to select, sei'd wheat. 



CACAO PRODUCTION IN BRAZIL. 



About one-fourth of the world's supply of cacao is 

 now produced in Brazil, and of the total output from 

 the country, the State of Bahia produces about 80 per 

 cent. 



Ill 1907. the export of cacao from Hahia was ecpial to 

 1^1,221 tons, or 1,743 tons less than in 1906. In the British 

 ('(inxiilar Report on the trade of Bahia for the past year, it i.s 

 mentioned that the 1907-S cro|i totals over 22,000 tons, thus 

 showing an advance of about 1,000 tons on the returns of 

 1907. 



As in other cacao-producing countries, the market price 

 of cacao at Hahia underwent cou.siderable variation in 1907. 

 While in the previiais year, Bahia cacao of 'fair' quality had 

 stood constant at about £2 6.1.. per bag of 132 lb., the price 

 rose as high as £5 llj.-. 6'/. at one time in 1907. A consider- 

 able falling off in the demand was the result of this high 

 figure. 



When the financial crisis of last year occurred in the 

 United States it had the effect of dimini.shing the price of 

 cacao, which fell to £3 (><. per bag of 132 ft). At present the 

 price of Bahia cacao of 'fair' <juality stands at £3 1.5.s-. to 

 £-1 per bag, but the demand for the product is still much less 

 than that which formerly existed. 



