Miscellaneous* 



lb 



[July, 1909. 



Kinamarkt. do. 6. 10. 1908, p. 725. 

 De positie der Kinamarkt. do. p. 725. 

 Java Cinchona market. Chem. and 



Drug. 24. 10. 1908, p. 651. 

 De wereldproductie van Kinabast en 



de marktpo*itie. Ind. Mere. 2/, 



10 1908, p. 782. 

 Cinchona and quinine. Chem and 



Drug. 14. 10. 08, p. 755. 

 Cinnamon. — 



Ceylon cinnamon and the foreign 



markets. "T.A."Jan. 190(5, p. 834. 

 The cinnamon market, do. p. 835. 



Distillation of cinnamon oil. Ind. 



Forester. Feb. 1908, p. 88. "T,A." 



June 1908, p. 525. 

 Eenmijcgal op Cinnamomum zeylani- 



cumBrergn. Cultuui gids 10. II. 109. 

 Cinnamon oil Industry in the 



Seychelles. Agr. News. Nov. 08. 



p. 365. 



HEREDITY. II. 

 By R. H. Lock. 



In our first paper on this subject 

 published in the Tropical Agriculturist 

 for June, 1909, an attempt was made to 

 explain the method by which simple 

 unit characters are passed on from 

 parents to their offspring. We have 

 now to show how, by the application 

 of this knowledge, a number of problems, 

 which have baffled students of breeding 

 for many centuries, are capable of a 

 reasonable and comparatively simple 

 explanation. 



It may be well to summarise briefly 

 the points which are now to be taken 

 as understood. 



Supposing by any possiblity two pa- 

 rents were to breed together whose 

 hereditary endowments were in every 

 respect identical— the parents being 

 alike not only externally, but in all the 

 inward essentials of their nature— we 

 should expect the offspring to be exactly 

 like the parents except for such points 

 as might be modified by differences of 

 education and external conditions. 



As a rule, however, the two parents 

 are not alike, and the student of 

 heredity is concerned with the problem 

 of how those points or characteristics 

 iu which the parents differ, are passed 

 on to future generations. 



We are usually concerned with a pair 

 of simple alternatives. To take an 

 extreme case, one parent may be black 

 and the other parent may be white. 



In such a case Ave suppose that the 

 black parent has something in it -a 



black factor— which causes it to appear 

 black, whilst the white parent contains 

 a white factor. 



The offspring of such a pair will con- 

 tain both factors, black and white — 

 and its appearance will depend upon 

 the relative power of the two factors. 

 In many cases the black factor com- 

 pletely overpowers the white, and the 

 mating results in the appearance of 

 exclusively black offspring. Although 

 the white factor is present, it is invisible. 



In the reproductive elements of these 

 last individuals, the black and white 

 factors separate completely. There are 

 produced pure "black" reproductive 

 cells and pure " white " ones in approxi- 

 mately equal numbers. 



When two such individuals are mated 

 together, therefore, the offspring may 

 arise either from 



a black male call meeting a black female cell 

 black „ „ white „ 



white ,, „ black ,, 



or a white ,, white female cell 



In consequence of this there will 

 appear on the average one pure black 

 individual, one which is pure white, and 

 two which contain both factors just as 

 their cross bred parents did. 



A pure black individual is one which 

 will breed true to its proper character 

 when mated with a similar individual ; 

 and the same thing holds good in the 

 case of a pure white individual. 



A factor which is able, like the black 

 one, to overpower its rival, so that any 

 individual which contains it shows the 

 black character externally, is known as 

 "domiuant"; whilst a character like 

 the white one which may be present 

 though invisible is called " recessive." 



We have yet to consider what happens 

 when parents are mated which differ in 

 more than one pair of factors. It will 

 be convenient to designate these factors 

 by letters. B and b are the two alter- 

 native factors of one pair ; A and a those 

 of another. Suppose a parent bearing 

 the two dominant factors A B is mated 

 with one bearing the two recessive 

 factors a b. Suppose we are concerned 

 with a species of plants in which A repre- 

 sents the character redness and B blue- 

 ness of the flowers, whilst a and b re- 

 present the absence of colours res- 

 pectively. Then A B will have both the 

 red and the blue character and will 

 appear purple, and a b will be white. 



The offspring of the cross will also 

 have purple flowers AB ab. 



The cross bred plant produces the 

 following different kinds of reproductive 

 cells AB, Ab, aB, ab. According to the 

 rule explained in a previous paper, half 



