270 



THK FLOWER. 



the bud. This must almost necessarily occur wherever the parts 

 are inserted at distinguishably different heights, and is the natural 

 result of a spiral arrangement. The name is most significant when 

 successive leaves are only partially covered by the preceding, as in 

 Fig. 207. Here they manifestly break joints, or are disposed hke 

 tiles or shingles on a roof, as the term imbricated denotes. It is 

 therefore equivalent to the spiral arrangement : and, on the other 

 hand, we properly apply tlie term imbricated to any continuous 

 succession of such partly overlying members ; as when we say of 

 appressed and crowded leaves that they are imbricated on the stem, 

 or thus express the whole arrangement of the scales of a bud 

 (Fig. 153), or a bulb (Fig. 172), or of a catkin or cone (Fig. 209). 

 The alternation of the petals with the sepals, &c. necessaiily 

 renders the floral envelopes likewise imbricated in the bud, taken as 

 a whole. But in proper festivation, what we have to designate is 

 the arrangement of the parts of the same floral circle (say the five 

 sepals or the five petals) in respect to each other. 



494. Now when the sepals or 

 ^s«:==5>. ><J=='°'^^°°V ^^® petals are three in number, 



^^' ^V^ /^^^^'^^^^\\ ^"^^ *''® regularly imbricated in 

 I I) I Ml yjll the bud, as in Fig. 437, the three 



/// \w^ /7/// ^^<'^'*'6s are arranged just as in 

 - yy ^^^^^ three-ranked phyllotaxis (238, 

 «7 438 Fig. 203) ; that is, with the first 



petal exterior to the others, the second is covered by the first on 

 cue side while it covers the third on the other. When they are five 

 (as in the calyx of Geranium, Fig. 439), they are disposed just as in 

 five-ranked or quincuncial phyllotaxis with the 

 axis shortened (240, Fig. 206) ; viz. two leaves 

 are exterior, two wholly interior, and one (the 

 third) with one edge covered by No. 1 on one 

 side while it covers No. 5 with its other edge. So 

 that this, 'the regular mode of imbrication when 

 the parts are in fives, is termed quincuncial a;s- 

 tivation, or the parts are said to be quincuncially 



FIG. 437. Diagram of a three-leared {trimerous) calyx and corolla, both imbricated iii 

 a}8tiTatiOD. 



FIG 438. Diaf^mm of the flestiTation of three petals (or one circle of the petals) of Blagiio- 

 Jia, similarly imbricated, but strODgly enwrapping, each making nearly a circle. 



FIG. 439. Diagram of the imbricative eestivation of the calyx and the convolutive scstiva- 

 tion of the corolla of Geranium ; the sepals numbered. 



