84 THE FLOWERING PLANT. 



Two sepals are occasionally found, as in the poppy, and this may 

 be here explained as a reduction from a higher number, probably 

 once possessed. In a good many flowers the perianth consists of 

 one whorl only, which is then considered to be, in most cases, a 

 calyx. In cases of doubt it is best simply to use the general 

 word perianth. Here again we see reduction. It is also to be 

 noted that in many small epigynous flowers (composites, umbelli- 

 fers, &c.) occurring in dense clusters, the calyx is very much 

 reduced in size, or even absent. Reduction may, lastly, be 

 carried to such an extent that both corolla and calyx are absent, 

 as in certain small inconspicuous flowers, like those of willow. In 

 the great majority of gymnosperms (fir, yew, juniper, &c.) no 

 perianth is present, but this does not appear to be a case of reduc- 

 tion from a former condition. 



Mention has still to be made of arrangement in the bud, 

 which, in the case of flowers, is called aestivation or prceffora- 

 tion, 1 and corresponds to the prsefoliation of foliage leaves 

 (p. 49). 



Cohesion. — The sepals are often quite free from one another, 

 as in rose, buttercup, and wallflower, when the calyx is poly- 

 sepalous or aposepalous. This is strikingly seen in poppies, 

 where the sepals are caducous, i.e., fall off very early. In many 

 flowers, on the contrary, the sepals are more or less united into 

 a tube. A gamosepdlous or synsepalous calyx of this kind occurs, 

 for instance, in the bean, primrose, and Canterbury bell. We 

 are here reminded of the cup-like or tubular structures formed 

 by connate leaves and sheathing stipules. 



. Adhesion. — According to the most modern views, the members 

 of other floral whorls adhere but seldom to the calyx. It may 

 not be amiss, however, to explain here some older ideas which 

 caused the invention of certain terms that are still current in 

 many books. The perigynous and epigynous conditions of the 

 flower have been explained (p. 81) as the result of the growth 

 of the floral receptacle into a cup-like structure, upon the rim of 

 which sepals, petals, and stamens are inserted (fig. 37). This 

 cup was formerly held to be part of a gamosepalous calyx, and 

 was therefore termed the calyx tube, the real sepals being looked 



1 The ways in which individual leaves are arranged have been defined in 

 the footnote to p. 49. Sepals and petals (as also foliage leaves) are disposed 

 in the bud with reference to one another as follows : — I. open, the parts 

 separated; II. closed, the parts approximated: (1) valvate, touching at the 

 margins; (2) overlapping at the margin; (a) imbricate, both margins of one 

 or more leaves covered ; (b) obvolute, every leaf with one covered and one 

 uncovered margin. 



These points may be determined by cutting through the bud trans- 

 versely 



