UNIT-CHARACTERS OF PLANTS 



151 



to have originated as sports and doubtless Mendelizing in 

 crosses. The cultivated celosias are good examples of i)lants 

 in which an excessive amount of anthocyan pigment pro- 

 duces brilliant red or yellow plants, the latter a probably 

 recessive sport from the former, just as the yellow fruit of 

 the tomato is known to be recessive to red fruit. In Coleus 



mica 

 DoddTttU/iilulifera 



jiilulifeTA 



Dodartii 



.'4 4 



41 HU *il4 II 



ten. 



Fig. 115. A Mendelian cross between two varieties of nettle differing in shape of leaf, I. Gen. = Fi. 

 II. Gen. = F2. III. Gen. = F3. The diagram indicates that the serrated form is dominant, the re- 

 cessive form reappearing in F2 and breeding true in F.3. (After Correns.) 



the red has a mosaic and highly variable distribution on the 

 green leaves, like that of yellow spotting in mammals. 



4. Colors of fruits and seeds. The colors of fruits and seeds 

 vary discontinuously in the same way that the colors of 

 flowers, leaves and stems vary. As an example we ma}^ con- 

 sider some variations in the color and composition of the 

 seed of maize. The common varieties of corn are either 

 yellow or white seeded, the yellow grain containing a yellow 

 colored endosperm, a character dominant to white. A black 

 pigment which is present in the aleurone layer just under the 

 seed-coat is responsible for a dominant variation in some 



