338 



HUTCHINSON'S POPULAE BOTANY 



FIG. 412. HENBANE. 



Urceolate persistent calyx. 



Against winged insects a more or less inflated 

 calyx is often a first-rate protection ; for besides 

 putting them to the labour of gnawing through 

 the calyx before the proboscis can be inserted, it 

 serves to hold them at a distance even when that 

 difficulty has been surmounted. Take, for in- 

 stance, the sack-shaped (saccate) base of the 

 calyx of Honesty (Lunaria, fig. 415), and con- 

 ceive how difficult it would be for one of the 

 smaller tissue-gnawing insects to get at the in- 

 terior of the flower. To bite a hole large enough 

 for the insertion of its proboscis would not be 

 sufficient ; the hole would have to be widened till 

 it was large enough to admit the insect itself, 



otherwise the little plunderer would be too far off to reach the nectar. 

 In flowers where the inflation of the calyx is greater, the difficulties of 

 gaining access to the interior are, of course, proportionately increased. 

 We must not stop to particularize, though the globose calyx of the 

 "Winter Cherry, to which we referred a moment or two ago, would 

 afford a ready illustration. The whole subject will be before us again in 

 the next chapter, when we shall deal with the contrivances in flowers 

 for the exclusion of unbidden guests, one of the most fascinating of 

 botanical themes. 



The other forms of calyx which remain to be spoken of may be treated 

 in connection with the forms of the corolla, to which we now invite 

 attention. 



Let us commence with a perfectly symmetrical or regular flower that is 

 to say, one the halves of which, produced by all 

 possible sections, are similar ; such, for example, 

 as the Wallflower (Cheiranthiis ckeiri). Here we 

 have a calyx of four sepals, two overlapping the 

 edges of the other two so as to form a sort of 

 false tube (a true tubular calyx may be seen in 

 the Primrose Primula vulgaris), and these serve 

 as a support to the four clawed petals, which, it 

 will be noted, are arranged in the form of a 

 Maltese cross. Hence, the corolla is described as 

 cruciform. It would be going too far from our 

 subject to show how the several correlated points 

 of structure in this flower are connected with its 

 pollination by insect agency ; but we may just 

 notice how admirably the cruciate corolla is 

 adapted as a landing-stage for nectar-seeking 

 visitors. 



FIG. 413. Pternandra cordata. 



Flower-bud showing (p) petals, 

 (c) calyx, (r~) receptacle. 



