348 ME. E. F. WILLIAMS 0~$ THE GENUS DIANTHUS. 



of the triplasic character of stipule, petiole, and scale. The upper- 

 most leaves, distinct from the calyx, by some authors called 

 bracts, are but squamiform modifications of the true foliage- 

 leaves. The true hypsophyllary leaves occur immediately be- 

 neath the floral organs, where they form an epicalyx of bractei- 

 form scales, generally in two pairs. 



Bracts. — These organs, above referred to, are very variable in 

 form, texture, colour, and number. The number is not always 

 constant in the same species, and where there are three pairs, 

 the inferior pair are always longer and narrower than the other 

 two pairs, thus approximating in form the uppermost leaves. 

 The study of the bracts themselves as a link in the continuity of 

 the nutritive and reproductive organs exhibits remarkable rela- 

 tions. Growing close under the perianth, they form part of the 

 flower ; they resemble the leaves in their decussate arrangement, 

 and the petals in their general contour. In their colour and 

 texture they exhibit also transitional characters : sometimes her- 

 baceous, like the foliage-leaves, sometimes stramineous or coria- 

 ceous, sometimes tinted purple or red, like the petals and calyx- 

 teeth. They are generally four in number to each flower, but 

 vary from two to sixteen ; when there is but a single pair, they 

 rather approximate in form the foliage-leaves. It also appears 

 that one of their functions is to protect the delicate tissue of the 

 calyx from perforation by insects attempting to reach the nectar 

 from below, instead of approaching from above the flower, and 

 by this means brushing the anthers and fertilizing the ovary. 

 Bracts with mucronate points are generally closely applied to the 

 tube of the calyx, whilst those forms with acuminate points are 

 usually patent. The length of the bract is determined rather 

 from its aristate prolongation than from the length of the lamina. 

 How closely the differentiation of the appendages of the essential 

 reproductive organs is related to the form and variation of the 

 nutritive organs, is seen in those cases where groups of organs 

 or of their appendages are transformed into those of next higher 

 or lower type under changed conditions of environment. They 

 may inclose but )- of the tube of the calyx as in D. suhacaulis, 

 or they may extend beyond it as in D. glacialis. They may be 

 small rounded scales as in D. Caryopliyllus, or slender awn-like 

 appendages as in D. atomarius var. setisquameus. 



The Flower. — The morphology of the entire plant, and particu- 

 larly of the flower, is that most favourable to entomophilous 



