312 



The Living Plant 



for the nectar, when the anthers open and shed new pollen on 

 their bodies. Then the nectar-secretion ceases, and simulta- 

 neously the hairs in the throat, hitherto impassable in an up- 

 ward direction, wither up, and the insect hies him away with his 



load to another one of the 

 flowers. Finally the flower be- 

 comes partially closed at the 

 mouth, as the second figure 

 shows, and droops on its stalk; 

 then it is sought no more by 

 insects, whose visits would ob- 

 viously be useless. 



Another common European 

 field plant, sometimes seen in 



Fig. 112.— A Salvia flower (substantially like OUr gardens, is that Mint 

 .S'. pratensis), in general visw and in sec- n i o 7 • _< • i 



tion, showing the mode of cross poUina- Called ^aivia pratenSlS, WflOSC 



tion described in the text. The line on the jnch-loug, bright-blue, hoH- 

 sections indicates the direction 01 thrust of 07 o ; 



the insect's proboscis. (Copied, with slight ZOUtally-Set, irregular floWCrS 

 simplification, from the Chicago Textbook.) 



possess stamens remarkably 

 hinged on their stalks (figure 112). These stamens are con- 

 structed on the principle of the lever, with the long arm 

 carrying the anthers up inside the upper lip, and the short arm 

 resting down like a valve over the entrance to the nectar tube. 

 The cross pollinators are bees, and when one of these insects, 

 coming to a pollen-ripe flower, alights on the lower lip, which is 

 suitable in size, form and position for its reception, it pushes its 

 head into the tube for the nectar and thus forces back the short arm 

 of the lever, which, swinging on the intermediate hinges, brings 

 down its longer pollen-laden end on the back of the bee in just the 

 position where that insect is struck by the overhanging stigmas 

 as it enters another flower that is ready for fertilization. 



One of the most wide spread of American Orchids is the little 

 wood-dwelling Habenaria orbiculata, which sends up a long loose 

 cluster of greenish-white flowers from two glossy round leaves 



