viii HEREDITY 133 



Fig. 54 is reproduced in Fig. 55. The Ledgers collect the 

 data from all plants of a family under the head of each 

 character separately ; this is conveniently done in the form 

 of frequency polygons, in which the number of each 

 individual is written; Fig 48 reproduces a page of the 

 ledger dealing with the height of the offspring of a plant 

 which was brother to that shown in Figs. 54 and 55. The 

 polygons elsewhere reproduced have had the component 

 plant-numbers omitted in order to save space. Lastly, a 

 Card Index of the completed ledgers enables any fact about 

 any plant to be found immediately. 



ii. Qualitative Characters 



Those characters which are not easily subjected to 

 statistical expression are dealt with in this sub-chapter. 



The Leaf-spot. The development of anthocyanin in 

 the leaf, which finds its fullest expression in the Red-Leaf 

 sports, is usually noticeable at the point where the petiole 

 begins to branch into the main veins. In Uplands, and 

 in Hindi, this leaf-spot is conspicuous, and forms a useful 

 diagnostic character in the seedlings for comparison with 

 Egyptians, whose leaf-spot is fainter, smaller, and pink 

 rather than crimson. The character varies with the water 

 equilibrium and illumination of the plant, like all antho- 

 cyanin characters. The F! of the "spotted by relatively 

 spotless " cross bears an intermediate spot. In F 2 the 

 ratio of the three forms accords closely with 1 : 2 : 1. 

 Extracted full-spot and spotless breed true, without known 

 exceptions. 



General colour of the leaf. The Upland cottons 

 possess a leaf lamina of much lighter hue than the 

 Egyptians. This difference in colour is real, and inde- 

 pendent of differences in hirsuteness, &c. The inheritance 

 of the character, or character-complex, is unknown, except 

 that large families have been found to breed true to one 

 or the other colour after F 2 . 



