SUPERPOSITION OF SUCCESSIVE PARTS. 195 



flower-cluster is surrounded and at first enclosed by an involucre 

 in the form of a cup, which imitates a calyx ; and the lobes of this 

 cup (the free tips of the calyx-leaves) in the present species are 

 bright white, so that the}- exactly imitate petals. Here, then, is 

 a whole cluster of extremely simplified flowers, taking on the 

 guise of and practical!}- behaving like a single flower, the invo- 

 lucre serving as calyx and corolla ; the one-stamened male flowers 

 collectively imitating the audroecium of a polyandrous blossom, 

 and surrounding a female flower which might pass for the pistil of 

 it. A series of related forms, from various parts of the world T 

 gives proof that this interpretation is the true one. 



356. Suppression of both Androacium and Gfynoecium. This 

 occurs in what are termed Neutral Flowers (347) , such as are 

 conspicuous at the margin of the cymes of Hydrangea (Fig. 293) 

 and of Viburnum lantanoides and Opulus, also at the margin of 

 the head of flowers of Sunflower, Coreopsis (Fig. 287, 288), and 

 the like. In these and most other instances, the perianth of 

 which only the flower consists is much larger and more showy 

 than in the accompanying perfect flowers : in fact, their whole 

 utility to the plant, so far as known, is in this conspicuousness. 

 No plant normally bears neutral flowers only ; but in cultivation 

 all sometimes become so by monstrosity, as in the form of Vibur 

 num Opulus called Snowball or Guelder Rose, also in "full 

 double " roses, pinks, &c. Occasionally flowers become sterile 

 and neutral by mere depauperation and abortion of perianth as well 

 as of essential organs, as in certain Grasses ; but such are 

 mostly vestiges of flowers rather than neutral blossoms. 



6. INTERRUPTION OF NORMAL ALTERNATION. 



357. Anteposition or Superposition is the opposition of succes- 

 sive (or apparently successive) whorls which normally alternate. 

 This result is brought about in different ways, some of which are 

 obvious, while of some the explanation is hypothetical. 



358. In the first place, there are cases of seeming anteposi- 

 tion, which are explained away on inspection. In a tulip, lily, 

 and the like, there is a perianth of six leaves and a stamen be- 

 fore each. The simple explanation is that the flower is not 

 6-merous, but 3-merous : there is a calyx of three sepals, colored 

 and mostly shaped like the three petals, which alternate with 

 these and are clearly anterior in the bud ; next, three stamens 

 alternate with the petals or inner circle of the perianth ; then 

 the three stamens of the inner circle, alternating with the preced- 

 ing, necessarily are opposite the three petals, as the first three are 



