The Origin of Wheat. 141 



the whole of southern Britain, represents the very' 

 earliest petal-bearing type in this line of development ; 

 indeed, save that its petals are now pinky-white, 

 while those of the original ancestor were almost 

 certainly yellow, we might almost say that the marsh- 

 weed in question was really the earliest petal-bearing 

 plant of which we are in search. It closely resembles 

 in appearance, and in the arrangement of its parts, 

 the buttercups, which are the earliest existing 

 members of the other or quinary division of flowering 

 plants ; and in both we seem to get a survival of a 

 still earlier common ancestor, only that in the one the 

 parts are arranged in rows of three, while in the other 

 they are arranged in rows of five ; and concomitantly 

 with this distinction go the two or three other dis- 

 tinctions which mark off the two main classes from 

 one another — namely, that the one has leaves with 

 parallel veins, only one seed-leaf to the embrj-o, and 

 an endogenous stem, while the other has lea\es with 

 netted veins, two seed-leaves to the embryo, and an 

 exogenous stem. Neverthless, in spite of such funda- 

 mental differences, we may say that the alismas and 

 the buttercups really stand very close to one another 

 in the order of development. When the two main 

 branches of flowering plants first diverged from one 

 another, the earliest petal-bearing form they produced 



