9T2 



PHENOMENA OF SEXUAL REPRODUCTION. 



another flower, the pollen is rubbed off its back on to the stigma. The cause of the 

 stamen springing out in this way is made sufficiently clear in Fig. 490 B. This shows the 

 short true filamentsyy which adhere by their bases to the sides of the corolla-tube, and 

 bear at their upper end the long connective c x, which oscillates readily about its point 

 of attachment. Only the upper longer and slender arm of each connective c bears an 

 anther-lobe a, the lower shorter arm x is without an anther, and is applied to that of the 

 other stamen in such a manner that the two form together a kind of arm-chair. When 

 the proboscis of the bee in search of honey penetrates the flower in the direction of 



Fig. 4go.— Salvia pratensis : a corolla with stigmas n and fertile anther-lobes a ; B stamens removed from corolla. 



the arrow, the lower arm of the connective is pressed down, and the upper arm"c is 

 made to move forward, and thus to strike the back of the insect. 



In the Pansy {Viola tricolor) we have quite a different contrivance for preventing the 

 possibility of self-fertilisation. In Fig. 491, A and B, is shown the position and arrange- 

 ment of the parts of the flower. The cavity of the flower enclosed by the petals is 

 completely filled up by the anthers and ovary, with the exception of the tubular spur of 

 the inferior petal in which the nectar collects, secreted by the appendages of the two 

 inferior stamens. The only entrance to this nectary, which therefore lies behind the 



Fig. 491.— Fzo/a tricolor: A longitudinal section through the flower (natural size); 5 the ovary fertilised and swollen ; 

 the filaments have been ruptured and the anthers drawn up by the growth of the ovary ; C the stigma with its orifice o and 

 lip Ip, on the style gr (magnified) ; / sepals, Is prolonged base of the sepals, c petals, cs spur of the inferior petals or 

 nectary; fs appendages of the two inferior stamens projecting into the spur, which secrete the nectar, a the anthers, 

 n stigma, v bracts ; D horizontal section through the ovary with the three placentae sp and ovules sK\ E horizontal 

 section through an unripe anther. 



reproductive organs, is through a deep channel in the inferior petal, lined with hairs. 

 The upper and lateral petals incline towards one another in front of the ovary which 

 is surrounded by the anthers, and above the channel in such a manner that the entrance 

 to it is entirely filled up by the capitate stigma B, n. The stigma is seated on a flexible 

 style (C, gr)^ is hollow and opens by an orifice which faces the hairy channel of the 

 lower petal ; the lower and posterior margin of this orifice has a lip-like appendage. 

 The anthers open of their own accord, and the pollen in the form of a yellow powder 



