32 



DIMORPHIC LEAVES IN RELATION TO HEREDITY, 



name "Culliiche." The species has not been definitely identified, 

 but Mr. F. L. Lewton su^^gests that it may represent Todaro's Gossy- 

 pium microcarpum variet}^ rvfum. The leaves of the Culluche cotton 

 are extremely variable in form, and many of them are quite simple. 



But instead of being broadly cordate 

 like the simple leaves of Upland or 

 Egyptian cottons, the simple leaves 

 of the Culluche cotton are fusiform or 

 lanceolate, much like the abnormal 

 leaves of the Eg^-ptian cotton shown in 

 Plate IV and text figure 15. One of 

 the simple leaves of the Culluche cot- 

 ton is shown in figure 17. Comparison 

 of this with the illustrations of the 

 Egpytian cotton previously mentioned 

 will show how close a resemblance of 

 leaf forms may arise in species of cotton 

 that are widely different in other 

 respects. 



RELATION OF DIMORPHISM TO MU- 

 TATION. 



Viewed as a phenomenon of heredity, 

 dimorphism of leaves presents an 

 analog}^ with mutative variation. The 

 fact that the abrupt change or contrast 

 of characters occurs in the same indi- 

 vidual plant instead of in separate 

 ])lants should increase the interest 

 attachmg to such variations, especially 

 if it appears that they are of the same 

 general nature as the mutations that 

 give rise to new varieties. 



The change of characters involved 

 in the production of dimorphic leaves 

 has the most direct analogy with the 

 rather rare })henomenon of bud muta- 

 tion. Cases arc known in which the 

 expression of characters is changed in a 

 single bud of a tree. A single l)ranch of a 

 tree shows a defmite peculiarity not 

 found in other branches or other trees of the same variety. A bud 

 mutation of coffee seen in Guatemala some years ago had leaves as 

 defmitoly unlike the remainder of the tree as any of the numerous 

 seminal mutations of coffee that had been previously studied. 



Fig. 17.— Simple leaf of Culluche cotton 

 from Tuxtla Gutierrez, Mexico. (Nat- 

 ural size.) 



