134 I'llYLLOTAXY, OR LEAF-ARRANGEMENT. 



their phyllotaxy. ami partly of tlu- \va\ in which they comport 

 when their margins meet in growth. Those leave- which are 

 within, or of higher insertion on the axis, will almost necessarily 

 IK- enclosed or overlapped: those which are members strictly 

 of the same whorl or cycle may fail to conn- into contact, or 

 may meet without overlapping at the contiguous margins or 

 apex; yet they may lie overlapped, since they may have grown 

 unequally or some a little earlier than their fellows. Conse- 

 quently, no perfectly clear line can be drawn in the flower between 

 cycles and spirals except by their mode of succession. More- 

 over, {estivation strictly so called should be concerned only 

 with the disposition among themselves of the several members 

 of one whorl, or of one complete spiral. So the alternation of 

 contiguous whorls, as of the three inner with the three outer 

 flower-leaves of a Lily or a Tulip (the alternative activation of 

 DeCandolle) , is a matter of phyllotaxy, not of ;estivatic n. The 

 latter is properly concerned only with the relations of each three 

 leaves to each other. 1 



_'.->:$. The proper aestivations may be classified into those in 

 which the parts do not overlap, and those in which they do. Of 

 the first, there are two kinds, the open (<est. 

 aperta] and the valvate, both chaiacteri/ed and 

 named by Brown. 2 Of the second, there is 

 one leading kind, the imbricate (adopted by 

 Brown from Linnaeus), with subordinate modi- 

 . fications. 8 Accordingly, the estivation is 



said to be 



256 254. Open or Indeterminate (tsst. a/ierta}, 



when the parts do not come into contact in the bud. so as to 



i The same applies to the two sets of sepals and of petals in Barl.erry, in 

 Menisperinum, and of the petals in 1'oppy, c. (359). 



- Liima'us, indeed, htt, " jEstivatio r,,lr,,l,t, si petala se expansnra instar 

 glun.a- icraminis poimntnr," the name, l.ut not tin- tiling': the glumes ..I 

 grasses are n..t valvate in the botanical sense. So the tern, as to its proper 

 use maybe said to originate with K. Brown. 



8 y,,V a brief discussion of "Estivation and its Terminology, see Amer 

 Jour. Sri. ser. :',. \. 339, 1875. 



As to names, it is perhaps more correct to say of the (estivation thai i 

 imbricative, convolutive, valvular, &c. (*t. imlrimtint, convdutiva, valvaris, &c.), 

 but of the leaves or pieces, tliat they are hnl^mtr, rniirol,,/, . valvate, &c., in 

 ffistivation , but such precision of form will seldom be attended to in botan- 

 ical descriptions. 



Kit: "". Uia./rammatic cross section of an unopened flower of Linden: its outer 

 circle .,f floral leaves (sepals) valvate in the bud; the inner (petals) between convol 

 and imbricate. 



