ORGANS OF REPRODUCTION. 



275 



5S9. 



forming a nearly flattened top as is usually 



the case when the number is small, frequently 



assumes a number of other shapes ; thus, 



in the Mairnolia and Tulip Tree, it becomes 



cylindrical (^Jig. 589); in the Raspberr}' {fig. 



591), Ranunculus {fig. 530), and Adonis 



{fig. 592), conical; in the Strawberry {fig. 



590), hemispherical ; while in tlie Rose {fig. 



439, r) the receptacle or thalamus, instead of 



being pi-olonged upwards as in the above 



examples, becomes hollowed out like a cup, 



or urn, and has the cari)els arranged upon its 



inner surface. These modifications of the 



thalamus, together with some others, will be 



more particularly referred to under the head 



of the receptacle or thalamus. The varying 



conditions of this portion of the floral axis 



necessarily lead to corresponding alterations 



in the mutual relation of the different whorls 



of carpels which compose an apocarpous pistil. 



Thus, Avhen there are two whorls of carpels 



placed upon a flattened thalamus, the inner 



have their ventral sutures directed towards the centre of the 



flower, while the outer have their ventral sutures directed to- 



Fifj. 580. Central part 

 of the flower of the 

 Tulip tree (Lirio- 

 dcndron tidipifera). 

 Tlie thalamus, a, is 

 more or less cylin- 

 drical; c. Carpels; 

 c, e. Stamens. 



Fig. 590, 



Fig. 591. 



Fig. 590. Section of the flower of the Strawberry. The thalamus is nearly- 

 hemispherical, aiul hears a number of separate carpels on its upper portion. 

 Fig. o91. .Section ot the ripe pistil of the Raspberry, showing the coni- 

 cal thalamus, I. Fig. j92. Pistil of Pheasaut's Eye {Adonis). 



■wards the backs of tlie inner carpels; or if there are several 

 whorls, the component carpels of each whorl are arranged in 

 like manner with regard to those within them. When the'thala- 

 mus is convex, or in any way prolonged upwards, the innermost 

 cari)els are upon a higher level than the outer; or when the 

 thalamus is concave, the outer carpels are uppermost. These 

 different arrangements modify very materially the appearance 

 of the flower. The mutual relations of the component carpels, 

 T 2 



