34 



ELEMENTS OP STIIUOTURAI BOTANY. 



style is long and slender. The examination of the ovary 

 requires much care; you will get the best idea of its 

 structure by taking one which has just burst open and 

 begun to discharge its seeds (Fig. 41). The outside will 

 then be seen to consist of four pieces (vcdves), whilst the 

 centre is occupied by a slender four-winged column (Fig. 

 42), in the grooves of which the seeds are compactly 

 arranged. The pistil thus consists of four carpels united 

 together, and is therefore synearpous. Every seed is 

 furnished with a tuft of silky hairs, which greatly facili- 

 tates its transportation by the wind. 



47. The Willow-herb furnishes an excellent examjde 

 of what is called symmetry^ We have seen that the calyx 

 and corolla are each made up of four parts ; the stamens 

 are in two sets of four each ; the stigma is four-lobed, and 

 the ovary has four seed-cells. A flower is symmetrical 

 when each set of floral leaves contains either the same 

 number of parts or a nrnltiple of the same number. 

 Observe that the leaves of our plant are net-veined. 

 The schedule will be filled up as follows : 

 . GREAT WILLOW-HERB. 



