464 ANGIOSPERMS less. 



Gymnosperms are seen. The modifications of the flower 

 among both groups of Angiosperms are almost infinite, and 

 can be thoroughly understood only by a careful study of 

 numerous forms : all that can be attempted here is to give 

 some idea of the essential points of structure and the lead- 

 ing modifications, by reference to a few selected forms. 



In a buttercup {Ranunculus), one of the most generalised 

 Dicotyledons, the flower is borne at the end of a long stalk 

 ox peduncle (Fig. 124, a and B, pd), the distal end of which 

 is expanded into a conical floral receptacle (b and c,fl. r), 

 serving for the attachment of the various parts of the flower. 



From the broad proximal end of the receptacle spring 

 five greenish leaves (a and b, cp), arranged in a whorl : they 

 are the sepals, and together constitute the calyx of the 

 flower. A little higher up arise, alternately with the sepals, 

 five larger leaves (a and b, //) of a brilliant yellow colour, 

 forming the conspicuous part of the whole flower : they are 

 the petals, and together constitute the corolla. Each petal 

 has at the base of its upper side a little scale called a nectary 

 (f, net), from which a sweet juice, called nectar, is secreted. 



Both sepals and petals spring from the base of the conical 

 receptacle. From the lower half of the part above their 

 origin arise a large number of stamens (b and c, st), arranged, 

 not in a whorl, but in a close spiral, and together constituting 

 the andrcecium. Each stamen (d) consists of a stalk or 

 filament (Ji), bearing at its distal end an expanded body or 

 anther {an), divided by longitudinal ridges into four lobes. 

 A transverse section (Fig. 125, b^) shows that each lobe 

 contains a pollen-sac or microsporangium {mi. spg), filled, in 

 the ripe condition, with minute pollen-grains or microspores 

 {mi. sp). 



From the distal portion of the receptacle arise, also in a 

 close spiral, a number of little pod-like bodies, the carpels 



