69 



of climate pr()l)al)ly changed its physical character sutH- 

 cientlj to alter the relative proportions of acids and alka- 

 lies, or even to develop a new element requisite for pro- 

 ducing the blue pigment. At all events, the tell-tale eye 

 stamps it as of foreign parentage, and we know from the 

 foregoing illustrations why the eye is yellow, and why one- 

 half of the style is also yellow and the other half blue ! 



Example 14. — The little Lobelia of a blue color, fre<iuent- 

 ly seen in hanging baskets, has for honey guides a pair of 

 diminutive white streaks at the throat, slightly diverging. 

 It is visited by a little bee a third of an inch long, and just 

 strong enough to force open the palate and enter for one-half 

 the length of its body, dragging its hind legs exactly over 

 the guides. These divergent little streaks therefore are 

 not exactly footprints, but im[)ressions of the insect's legs 

 as it lies flat and outstretched si[)ping the nectar ! 



Charles Darwin points out "a striking case of correlation 

 of color with a special organ," viz.: ''In many Pelargo- 

 niums the two upper [)etals in the central flower of the truss 

 often lose their patches of darker color: and when this 

 occurs, the adherent nectary is (juite aborted, the central 

 flower thus becoming })eloric or regular," etc. Well, that 

 is precisely what one would expect, no nectary no honey- 

 guide ! 



Darwin was a very busy man and he would not have l)een 

 long in flnding out all about the nature of honey guides if 

 he had only turned his attention to that sul)ject, but one 

 would judge from the quotation that he had not done so. 



Grant Allen in The Strand Magazine for April, 1899, 

 referring to white flowering plants, remarks as follows: "A 

 curious coincidence is, that none of them have any streaks, 

 spots, or lines on their petals. The reason is simple. 

 Such streaks or lines are ahvays^ honey guides to lead the 

 insect straight to the nectary " ! 



Anything that arrests attention may be useful as a guide 

 for insects. A large [)ro})ortion of the markings on flowers, 



