37° 



The Ohio Naturalist. 



[Vol. Ill, No. 4, 



ATAVISM IN THE WATERMELON. 



John H. Schaffner. 



In the summer of 1895 I noticed a peculiar variation in the 

 leaves of a watermelon vine, growing in a patch in Claj- county, 

 Kansas. The plants were of the variet}^ known as the " Georgia 

 Rattlesnake," and, excepting the single plant mentioned, were of 

 the usual type. 



The leaves of the watermelon seem to be quite constant in form. 

 They are usually described as palmateh' five-lobed, the lobes 

 being mostly sinuate-pinnatifid, with all the segments obtuse 

 (Fig. id). But in this plant the lobed condition of all the leaves 

 was almost entirely absent, the border being only moderately 



undulate (Fig. ic). 



Some of the seed 



\ArJ\|r 1 AW lis from this individual 



were planted in 1S96, 

 and the same leaf pe- 

 culiarity was report- 

 ed. The form has 

 been successfully cul- 

 t i V a t e d every year 

 since that lime, al- 

 though it was usually 

 planted in patches 

 with the ordinary 

 kind and much cross- 

 pollination nuist have 

 resulted. 



Whether this con- 

 dition of entire leaves 

 is common in the wa- 

 t e r m e 1 o n I do not 

 know, but I regard it 

 as a good example of 

 atavism, or reversion 

 to a more primitive 

 type. Such reversions 

 may perhaps be of frequent occurrence in the species. It is a 

 well-known fact that the leaves of many fossil plants from the 

 Cretaceons have entire borders, while the modern representatives 

 of the same genera are often serrate, denticulate or lobed. Turn- 

 ing now to the .seedling of the ordinary watermelon (Fig. la), 

 we find that the leaves develop in succes.sion from the entire to 

 the mature, lobed form. The cotyledons are oval and entire, 

 while the first leaf is almost an exact counterpart of the variety 

 under con.sideration. In the second leaf the lobed condition is 



Fig. :. 



a, A young seedling of the usual form. 

 d. Leaf of usual form, 

 f, Leaf of special form. 



