THE PEDIGREE OF WHEAT. 



665 



common plant in wet ditches and marshes throughout 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 ear- 

 liest petal-hearing plant of which we are in search. It closely resem- 

 bles in appearance, and in the arrangement of its parts, the buttercups, 

 which are the earliest existing members of the other or quinary divis- 

 ion 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 ar- 

 ranged 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 distinctions which mark off the two main classes from one an- 

 othernamely, that the one has leaves with parallel veins, only one 

 seed-leaf to the embryo, and an endogenous stem, while the other has 

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

 enous stem. Nevertheless, in spite of such fundamental 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 on one divergent 

 branch was the alisma, or some- 

 thing very like it ; the earliest 

 petal-bearing form they produced 

 on the other divergent branch 

 was the buttercup, or something 

 very like it. Hence, whenever we 

 have to deal with the pedigree of 

 either great line, the fixed historical point from which we must needs 

 set out must always be the typical alismas or the typical buttercups. 

 The accompanying diagram will show at once the relation of parts in 

 the simplest trinary flowers, and will serve for comparison at a later 

 stage of our argument with the arrangement of their degraded descend- 

 ants, the wheats and grasses. 



Our own smaller alisma has a number of ovaries loosely scattered 

 about in its center, as in the buttercups, with two rows of three sta- 

 mens outside them, and then a single row of three petals, followed by 

 the calyx or inclosing cup of three green pieces. Its close ally the 

 water-plantain, however, shows signs of some advance toward the 

 typical lily form in the arrangement of its ovaries in a single ring, 

 often loosely divisible into three sets. And in the pretty pink flower- 

 ing rush (not of course a rush at all in the scientific sense) the advance 



/? ' [> tllWdS 



,s\ 



Fig. I. a. ovaries ; 5, stamens, inner whorl ; c, 

 stamens, outer whorl; d, petals ; e, calyx-pieces. 



