Nice Construction of Flowers, 1 1 



These functions of the perianth are performed by it 

 either quite alone, or, more frequently, in conjunction 

 with special developments of the androecium and gyn- 

 secium. Many flowers thus become very complicated 

 machines, in which it is of the greatest importance that 

 each part shall work with perfect accuracy, that not a 

 piece of the apparatus shall be too long or too short, 

 shall get damaged or out of place, or become unfitted 

 for its office by the injurious effects of weather, or by 

 the attacks of animals. 



If a leaf be gnawed by an insect, and in consequence 

 suffer some loss of substance, or if a leaf undergo change 

 in its shape and size through gall-producing insects, 

 the performance of its function is thereby hampered, 

 but, as a rule, not completely stopped. Quite other- 

 wise is it with those floral organs which form a link in 

 the chain of fertilisation. Here the smallest and most 

 inconspicuous change in the size and shape of a part may 

 render the function of the whole apparatus impossible. 

 In Sternbergia and Colchicum, for example, when the 

 erect flower closes, as it does in the evening, the pollen 

 is pressed against the inner surface of the perianth, to 

 which it adheres, and by its intermediation is conveyed 

 to the stigma, which stands up above the anthers. 

 This is brought about in the following manner : — The 

 perianth increases in length during the blossoming period 

 by intercalary growth ; and this lengthening is just such 

 as to cause those spots on its inner surface, which, on 



