THE BUTTERCUP FAMILY, 



75 



of a carpel, showing the very young ovule at the base 

 of the ovary. (6) is a ripened fruit called an Etwrio, 

 or cluster of achenes. (7) is a single achene ; and 

 (8), one cut vertically, shows the seed now completely 

 filling the ovary, and invested Ijy the carpel, now 

 called the Fcricarp. The white substance is Undosperm, 

 sometimes called Albumen, and is the nourishment laid 

 up for the minute embryo lying 

 at its base. (9) is the embryo 

 detached. (10) is a side view of 

 it, showing the two cotyledons, 

 the rounded end being the radicle. 

 There is a species of Bcmun'- 

 culus which grows in ponds and 

 rivers, probably introduced from 

 Europe, called B. aquat'iUs (Fig. 

 27). It has white petals with a 

 yellow base. If it grows in still 



water, it bears two kinds of Fig, 27.— Leaves of the water 



, Crowfoot (Banun'cidus 



leaves: some are noatino- and aquaf msy. the tioiumg leaves 



^ complete ; the submerged 



completely formed, while others leaves, finely divided. 

 are under water. These are always* dissected or have 

 fine thread-like segments. 



This is a consequence of living submerged, as 

 many other water-plants of quite different families 

 have similarly dissected leaves. If the plant grow in 

 rapid streams, the dissected, submerged leaf is the only 

 kind usually formed. 



