CURRENT INVESTIGATIOiNS IN ECONOMIC BOTANY. (Continued front Vol. IV., page 11 1.) BY WILLIAM G. FREEMAN. SEMINAL SELECTION OF SUGAR CANHS.

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1 86 W. G. Freeman. CURRENT INVESTIGATIOiNS IN ECONOMIC BOTANY. (Continued front Vol. IV., page 11 1.) BY WILLIAM G. FREEMAN. SEMINAL SELECTION OF SUGAR CANHS. In the previous articles we have devoted some attention to budvariations or sports and chemical selection of the sugar-cane and indicated broadly the results of the efforts made to produce races of canes of higher sucrose yield by taking advantajje of variations, in the one case correlated with differences in external characteristics of the plants and in other to be recognized only as the result of chemical analysis of their juice. We now turn to the third method which is employed in practice, namely, seminal selection. The prosecution of work along this line possesses especial interest in the case of the sugar-cane owing to the fact that it was for long generally supposed that the sugar-cane did not produce seed. Thus Darwin in his " Variation of Animals and Plants under Domestication," remarks that the sugar-cane " which grows vigorously and produces a large supply of succulent stems, never, according to various observers bears seed in the West Indies, Malaga, India, Cochin China, or the Malay Peninsula." This view was held until as recently as 1887 in which year Soltwedel in Java proved that the plant did at times produce fertile seed. In the fouovv'ing year Harrison and Bovell in Barbados reported the discovery of sugar-cane seedlings found growing spontaneously in the fields, an observation which they confirmed in the following year by actually raising young plants from seeds. There are some grounds for supposing that sugar-cane seedlings were raised in Barbados about 1860 but it was not until that the independent discoveries in Java and Barbados definitely established the fact that the sugar-cane does at times bear fertile seed. The practical value of the discovery was at once recognized and an enormous amount of care and labour has been and is being devoted in many parts of the world to the raising of improved races of seedling canes. Progress has been slow owing to (1) the flowers of the plant being so small that controlled hybiidization is very difficult, and (2) the long period which intervenes between the first raising of a seedling and the pronouncement of the verdict as to whether the resultant plant is good or not. To deal with the latter difficulties first, let us summarize the

2 Current Investigations in Economic Botany. 8y cultural procedure in tbe West Indies. The parent canes flower or " arrow " in tbe dry season (about Novembei-) of one year, Tbe small seeds are sown in boxes covered witb glass, and tbe young seedlings after being pricked out into pots are ready for transplantation into tbe open ground in tbe following April or May. During tbe first year of their life growth is comparatively small and at tbe end of tbis period all tbat is possible is to select tbe more vigorous seedlinjfs for furtber propagation in tbe ordinary way by cuttings. At tbe end of tbe second year a small number of plants will be available grown from eacb of tbe original seedlings and tbose showing desirable cultural characteristics are selected, some of their canes crushed and their juice analysed. Tbe best are again propagated by cuttings and tbe plants selected by cultural and chemical characters. Tbe process is repeated and it usuall}' requires about six years before enougb plants are available to allow of plots of say 100 plants eacb, all derived from one original seedling, being grown on several different estates, or of one plot of perbaps ten acres being grown as an industrial experiment on a single estate. When it is remembered tbat in addition to tbe percentage of sucrose and glucose in tbe juice tbe value of a sugar cane depends on its ratooning properties (i.e. of developinj^ successive annual crops from tbe same rootstockaftertbepreviousgrowtbof stemsbavebeen ctit) on its resistatice to disease, on its milling characters, on tbe value of tbe crushed cane as fuel and numerotis other characters, and that acctii'ate knowledge on these points demands trial of each variety on an estate scale with plots of several acres in extent and for several years, it must be conceded that the practical difficulties confronting those engaged in tbe work are sufficiently serious to prevent rapid progress. In practice it is necessary to carry on the early selections in small plot experiments, rigorously rejecting eacb year all but the very best canes and finally testing tbe few survivors on a larger scale before recommending tbem to planters for trial on a sufficiently large scale to allow of an authoritative opinion being expressed. The following example from British Guiana will serve to illustrate the scale on wbicb seedlings bave been raised and the comparatively small number whicb bave passed through the selection ordeal. During the years 1896 to 1901 some 314,000 seedlings were raised, of which 75,000 were transplanted into baskets and some 19,000 cultivated in tbe fields, but the net result was that only 21 were finally recommended to planters for estate trial and of perhaps not more than three have stood the test of several seasons' trial and

3 88 W. G. Freeman. are now cultivated on an extensive scale not only in the West Indies but in other parts of the world. The other difficulty has been due to the small size of the flowers combined with the general habit of the plant. The inflorescence of the sugar-cane consists of a feathery plume not unlike that of the more familiar Pampas-grass, borne some 12 or 15 feet above the jjround, and consequently rigidly controlled hybridization as practised on flowers of large size and readily accessible appeared almost impossible. At first no selection was made at all, but any seeds whatever their parentage were taken and plants raised in the hope that some might prove to be of value. An advance upon this method was to select certain canes as parents and to collect seed from these only, but in these cases although the female parent was known the parentage on the male side was unknown and the result found in various parts of the world was that the majority of the seedlings were inferior to the plants from which they were produced. To ensure the best results it is essential that it should be possible to select both parents and various methods have been suggested and tried to ensure the crossing of chosen varieties. Adjacent plots, or alternate rows in one plot, ot two selected varieties know to flower at the same time were arranged but although some of the seeds produced were doubtless the result of cross pollination too much w'as left to chance to ensure very satisfactory results. Another method, easy to carry otit, was to ' bag' the infloresences of the selected mother canes and when the pistils were ripe to shake into the temporarily opened bags pollen from the infloresence ofthe other selected variety. By this means some, but not necessarily all the seeds would probably be the result of cross pollination between the two varieties. In 1894 Wakker discovered in Java that the Cheribon cane had practically unisexual flowers the pollen not being fertile, and Kobus planted plots witb alternate rows of this Cheribon cane and of an Indian cane, Cliunnee, with normal flowers. With proper precautions the fertile seeds must have been the result of the pollination of the Cheribon by the Chunnee, and several thousand hybrid canes were raised. In 1904 in Bai'bados Lewton Brain succeeded, under considerable practical difficulties, in actually emasculating and bagging inflorescences of one variety and definitely pollinating the flowers later with pollen from another variety. A few seedlings were raised

4 Current Investigations in Economic Botany. 89 of known parentage on both sides but details are not yet available as to their characteristics. The experiment is of great interest and importance as demonstrating that rigidly controlled hybridization of the sugar cane is practicable and steps are being taken by others to continue the work along these lines. Having now sketched the methods employed in the raising of seedling canes and the principal practical difficulties which have to be contended against it is desirable to review briefly the main results attained, and to do this it is desirable to look back a few years and note what were the conditions which gave an impetus to the raising of seedling canes. About twelve years ago the " Bourbon " was the standard cane of the West Indies and was very extensively cultivated, but it became very subject to the attacks of fungoid diseases, so much so that in some cases in bad seasons whole fields were rendered practically worthless. Effort was made to combat the disease and attention was early directed to the question of finding disease resistant varieties. In Barbados for instance in 1891 the variety known as Caledonian Queen gave good results on an estate where it had been planted along with the Bourbon although the latter canes were so attacked that they had to be destroyed. Seedling canes were also tried and at the experiment station at Barbados the seedlinjj B. 147 gave during the years 1894 to 1898 an average of nearly 2,000 lb. of sugar per acre over the yield of the Bourbon under similar conditions, the actual figures being B. 147, 7,190 lb,. Bourbon, 5,210 lb. Another seedling cane B. 208 has also proved itself of great value and these two varieties are now cultivated in the colony on an extensive scale, although the most widely grown cane at present is White Transparent one ofthe so-called " older varieties " of unknown origin. The Bourbon cane in Barbados has almost entirely disappeared. The two Barbados seedlings have not only given good results in the country of their origin ; B. 208 is according to Dr. Cousins " well suited to all parts of Jamaica and is probably the best cane now available." It has also given good results and proved of considerable economic value in Antigua, St. Kitt's and Nevis, in British Guiana, and as far afield as Louisiana and Queensland. Seedlings of high value have also been raised in British Guiana (these are designated by the letter D) and again quoting Dr. Cousins " D. 95 has [in Jamaica] proved a great success. This cane has give double the yield of crystallized sugar per acre, as compared w ith the Jamaica cane and upon a commercial scale."

5 90 Current Investigations in Economic Botany. Much more evidence might be called, but the above will probably be sufficient to prove that seedling canes have proved to be a factor of great economic importance in raising the sugar industry of the West Indies from the depressed condition into which it had fallen, due in considerable measure to the prevalence of fungoid disease which attacked the old standard varieties from about 1894 onwards. The great expectations once held of seedling canes may not have been realized, and the evidence available indicates tbat perhaps about 25 per cent, is the maximum amount of sugar which sugarcanes will yield and be profitable. Increase of yield beyond this point must be sought rather by increasing the tonnage of the canes than by attempting to enhance their sucrose contents. Disease resistance may be only relative. It must be remembered that in the case ofthe older canes propagation by cuttings from canes permeated with fungal hyphae ensured the continuance ofthe disease as each cutting carried the disease within it and had not to wait for infection. With seedlings a new race was started free at first from disease but as this stock, like the former, is propagated year after year by cuttings the diseases will probably be propagated too, so that in the course of a few years another new race would be required to ensure a relatively disease free stock. The greatest hope for the future lies in the expectation that it may become increasingly practicable to raise canes of definitely known parentage from carefully selected plants possessing to the greatest degree the characteristics of disease resistance, high sucrose yield, heavy tonnage of cane and the other properties which have been previously mentioned as marking a sugar-cane of high economic value.

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