60 



ORGANOGRAPBY. 



flowers are the Gentians, Epilobium, Campanula, Parnassia, 

 Lobelia, etc. The anthers in Lobelia are like those in the 



Sunflower family, that is, 

 syngenesious, or united 

 by their anthers forming 

 a tube around the upper 

 portion of the style. The 

 pollen is discharged while 

 the style is yet so short (Pig. 137) as to be concealed deep 

 down in the tube. As the stigma approaches maturity, 

 the style elongates and pushes the pollen out before it ; 

 the mouth of the tube is so situated that insects entering 

 the throat of the corolla, for the purpose of getting nectar, 

 would necessarily brush the pollen onto their body from the 

 end of the protected stigma (Fig. 137a). The stigmatic sur- 

 face finally becomes exposed (Fig. 138). It is evident from 

 the description and figures that self-fertilization is impossi- 

 ble; and cross-fertilization by the insects, which transport 

 the pollen from flowers in the first stage of maturity to 

 those in the second stage, must take place. 



77. Dimorphism (Gr. di, two ; morpha, form) denotes 

 two kinds of hermaphrodite flowers of the same species. 

 It is often an adaptation for intercrossing. An example is 

 furnished by the Houstonia. 

 One set of flowers has long 

 stamens and a short pistil _ 



(Fig. 139), and the other l^^^'^S^^\ ^-J 

 set has short stamens and xi. 



a long pistil (Fig. 140). 133 issa 



Figs. 137, 138. Prolerandrous flowers oi Lobelia syphilitica: 137. First stage; 

 Anthers mature; 138. Second stage; Stigma mature; an, anthers ; _/?/, filament; 

 st^ stigma ; h, hairs. Figs. 137a, 138a : Stigma slightly magnified. 



