The Nature Column.

Digger (Invercargill RSA), Issue 35, 12 November 1920, Page 11

The Nature Column.

(By "Student.")

("Student" will be pleased to receive notes on any bramch of Natural History. Observations on birds, insects, plants, etc., will be equally welcome. If using a pen-name, will correspondents please enclose real naine and address.) In his Principles of Evolution published a few years ago Joseph McCabe rather discounted Menddlism and stated that only a sraall thou.gh distinguished minority of embryolcgists, zoologists and botonists - accepted the theory. Nowadays it is heing more and more widely accepted and lateiy it is helieved to have settled the question of inheritance of sex. Mr F. W. Keeole, F.R.S., says of Men. del : "Thanks to the genius of this man we know that if v»e will discover the laws of inheritance we must fix our atten-t-ion not on the organism as a whole out upon one and another in turn of the many attributes or characters of that organism Mendel diseovexed the si'mple laws which govern the mode of inheritance of the characters or attributes of living things." The ceils of all living things -arise bysubdivision of the original germ cell, and these cells each contain what may be described as a set of characters in duplicate. The reproductive cells however have only one s,et of characters each. The fusion of the male and female oells thus produce 'another duplicate cell, but this cell contains the characters of both parents. Som& of the main conclusions reached by -Mendel are as foilows : — The first is that as the individual derives from two parents and is in .that sense a dual thing so it is dual with repect to each cf its characters. It may derive the means of developirg any one character from both of its parente. If so it is pure bred and mating with its like will have issue, all of which will exhibit the character in question. If it descend from parents one of which possessed the character and the other did not, the individual is load,ed with but one charge for the expression of character, and though the one charge is sufHcient to show the character in the individual it will not be sufficient to establish the character in all the descendants. Mated with another like individual only half charged with a particular character, the offspring produced will have a fixed proportion having the character in question and a fixed proportion which will lack it. The germ cells which as before stat^| are units ana join together in pairs produce the individual, however, which carries a full double charge gives rise to germ cells all alike with respect to this character. They are all charged with it. The individual ear. 1 rying oue charge gives rise to germ cells half have the charge and half lack it. When the germ cells of two such similar individuals units in pairs the result can be predicted. On the average in four unions one will be between germ cells charged with the power of developv.ng a certain character, two between cells one of which is charged and one is not, . and one between un charged germ cells. The first combination will produce a-n individual pure to the character and mated to a similar individual will produee the same character. The second combination will produce an individual which may show the character, but the progeny will hetray his Uybrid nature for mated with a similar individual the offspring will be divisible into haves and have-nots as before described. The third combination will result in an individual lacking the character, and uiiion with a like individual will result in progeny all of which will lack the character, and insofar as this lack of character is concerned they are purebred. Mendelism is the foundation stone of the plant breeder. If he is seeking a new breed of. wheat, he does not now rely on chance matings, but works with a definite end in view. Professor Biffen, F.R.S., of Cambridge, stresses this point, and was one of those who worked to have Mendels principles tested out. Recognising that the yield of wheat was governed by factors such as immunity from disease, stiffness of straw, and that hetter baking qualities were wanted, experiments were set on foot to try and combine these factors in one breed. Having by selection found a wheat which was rust proof it was crossed with the most susceptible variety. The first generation F2 in the following season made it clear that the power of resisting rust was an inheritable character, for among a mass of afflicted plants one could distinguish plants which were not affected. These rust resistant plants were in the proportion of one to three, agreeing with Mendel's laws. They snbsequently bred true to the rust resistant chawteter. a largo number ot experiments of a similar kind were pnt in operation and one of the results has

been to produce a wheat stiff in the straw, rust resistant, and possessing better baking qualities than wheat previously raised in England. Professor Biffeai, says ; "We have measured Mendel's principles from the economic standpoint and know that once there is proof of the independent inheritance of any character then it can be worked up into any combinations one requires.