Vol. X. No. 241. 



THE AGKICULTUKAL NEWS. 



227 



SUGAR INDUSTRY. 



CROSS-POLLINATION OF THE 



SUGAR-CANE. 



Interesting information in connexion with the flower of 

 the sugar-cane and with the methods in use in Java for pro- 

 ducing hybrids therefrom lias been published in Mededeelin- 

 gen van Het Proefstadon voor de Jat'a-Suikerindustrie, No. 6, 

 entitled De gcslachtelijke Voortplantiiig bij het Suikerriet, 

 bj- G. Wilbrink and F. Ledeboer, the contents of which have 

 been translated and abstracted by Mr. .T. Lei}', Chemist to 

 the Antigua Sugar Factory. It is from this abstract that the 

 following information is taken. 



The flowers of the sugarcane require moisture to enable 

 them to open; arrows that are at all dried up will not flower. 

 Flowering commences when the arrow is pushed out of the 

 sheath — an event which may occur early in the season, or 

 later, according to circumstances. The flowers themselves 

 commence to open early in the morning, even before sunrise, 

 and continue to do so, in Java, until about 8 a.m. It has been 

 noticed that the fir.st arrows to open are the stronger ones, 

 while the first flowers produced on the arrow are al.so the 

 most vigorous. As is now well known, certain varieties of 

 the sugar-cane produce little, if any, fertile pollen; though 

 abortion of the female organs is rare The pollen iiself con- 

 sists of small yellow balls, each of which has a thick outer 

 wall of a corky consistency and a tliin inner meml)rane. 

 There is an aperture in the outer wall through which the 

 pollen tube is extruded on germination. Healthy pollen 

 grains contain starch — a fact Avhich is made use of in testing 

 their fertility, in the following manner. ,\ nearly rii)e anther 

 is opened with a needle in a solution of iodine in potassium 

 iodide. The iodine imparts a blue colour to the starch in the 

 pollen, if it is present. If starch is not present, ths pollen is 

 infertile. By this means, after testing the pollen in several 

 anther.s, it is possible to determine if any given variety of the 

 cane possesses fertile pollen. (See also At/ric'idliiral News, 

 Vol. IX, p. 19."-).) 



Three methods for securing cro.ss-pollination are describ- 

 ed, in all of which a variety producing [iractically no fertile 

 pollen is used as the female parent. According to the first 

 method, the two varieties to be crossed are planted in alter- 

 nate rows and arrows of the male variety are bent 

 over, so that each occupies a position a little bit above, 

 and to windward of, an arrow of the female variety. 

 Bent sticks are tied below the growing joints of the male 

 arrows, to prevent their breaking liy lengthening. Further- 

 more, the male arrows are cut soon after they have been used, 

 in order to preclude the contamination of the female arrows 

 through seeds from the male arrows being blown into them. 

 This natural method of crossing is simple, and gives rise to 

 many seed.s, but it can only be employed with varieties pro- 

 ducing numerous flowers. 



Another method employed is as follows. Male arrows are 

 cut two or three days after they have commenced to flower, 

 and are placed in a bamboo joint filled with water. The 



cutting takes place before sunrise, and one or two joints 

 of the top of the cane are left attached to the arrows, 

 in order that they may remain fresh for about two 

 days. The bamboo pot is then tied to the female arrow 

 in such a way that the male is above the female, and on 

 the windward side. This operation is conducted when 

 a few flowers at the top of the female arrow are open, 

 as it is then certain that several will be open on the 

 succeeding morning; it must be performed before the sun has 

 any power. When much of this work has to be done, 

 it is commenced in the late afternoon, or better, in the 

 evening. 



A further method for securing cross-pollination is to collect 

 the pollen on a glossy paper, and subsequently to convey it to 

 the stigmas of the female flowers by means of a soft brush. In 

 order to obtain the pollen, the male arrow is bent down, on 

 one evening, and on the next morning, as soon as it is dry, the 

 arrow is well shaken over a piece of paper, from which the 

 pollen is transferred to a small box. or a watch glass, lined 

 with a fresh piece of leaf, or a moist piece of filter paper. 

 This method, however, has not proved very successful. 



AVhen it is desired that the parentage of the seedlings 

 shall be known with certainty, it is necessary to surround the 

 female arrow with a screen. This is because the pollen 

 is often carried a long distance by the wind. For the purpose, 

 a special form of apparatus is employed, in Java, having an 

 opening on the lee side, provided with a double over-lapping 

 cover. The male arrow is introduced through this opening, 

 preferably when there is no wind. It is interesting to note 

 that some varieties do not give a good yield when fertilized 

 within a screen. 



The best method of collecting the seed has been found to 

 lie to surround the female arrow with a small muslin bag in 

 which the seeds are allowed to ripen — a process occupying 

 from two to three weeks. The seeds are allowed to dry for 

 one to two days in the bag; afterwards all the ears are stripped 

 from the arrow and sown at once in pans. The.se are 24 

 inches wide and 16 inches deep; they are half filled with rich 

 mould, on the top of which is placed a mi.fture of dry sifted 

 horse-dung and fine sand in equal quantities, forming a layer 

 G inches deep. 



All the seeds arising from one arrow are sown in one 

 pan, unless they are too numerous, when two or three pans 

 are used. The seeds are pressed down on the wet sand, but 

 are not covered; they are carefully watered in the morning 

 and evening, and are protected with a loose covering of trash 

 when a shower is expected. They are exposed to full sunlight 

 from the first. If there are no results at the end of fourteen 

 days, it is certain that no fertile seeds have been produced on 

 tbe arrow. In cases of success, the young plants are planted 

 out, when 8 inches high, in pots 10 inches deep by b inches 

 wide, filled with mould. One month later they are trans- 

 planted into the ground, being removed from the pot with 

 the mould. If they are planted directly in the ground, on 

 removal from the pans, large numbers of tbe seedlings die. 



It should be noted that, while the methods described 

 furnish an excellent means of obtaining numerous seedlings 

 whose parentage on both sides is known with approximate 

 certainty, yot none of them is sufficiently exact for con- 

 ducting hybridization work on strictly accurate Mendeliau 

 lines, since none of them entirely jirecludes the po.ssibility of 

 the occasional formation of self-fertilized seeds on the female 

 arrow through the agency of the fertile pollen grains which 

 may occasionlly be produced in the anthers of varieties 

 whose pollen is usually sterile. 



