218 COMPENDIUM OF GENERAL BOTANY. 



are in the same horizontal plane, " vertieillate." Example: the 

 Liliijlone. 



2. Acyclic flowers : spiral arrangement of the floral leaves. 

 Example : Magnolia. 



3. Ilemicijclic flowers : the floral organs may in part he. sj)irallj 

 arranged (especially the calyx) and in part verticillate. Example : 

 Jianunculacem. 



The calyx usually forms one circle of floral leaves ; the corolla 

 also one ; the androecium one or two ; the gynoecium usually one. 

 For causes more or less associated with the mechan- 

 ical theory of phyllotaxy there is often noticeable 

 an alternate arrangement of members of the vari- 

 ous verticillse, provided they occur in equal num- 

 '^,^^1^^^^' bers (see Fig. 139). The whorls or verticillte may 



Fig. 139.— Dia- also be opposite, as shown in Fiff. 140. 

 ffram of the * /• i t ^ i 



flower of Lili- A further discussion oi these relations would 



(After Krass and ^^^^ \e2i^ US to that Stage of investigation in which 

 Landois.) ^j^g comparative morphology of flowers seems to 

 give evidence of the transmutation of one genus into another. 

 "We will cite an example. Kormally the ScrofulariacecB have five 

 stamens; Veronica has two; Gratiola has two 

 normal stamens and two sterile structures, the so- 

 called ' ' staminodia. ' ' Digitalis and Scrofularia 

 have four stamens and one staminodium. It is 

 evident that the abortion or the suppression of stamens 



plays an important part in the cases mentioned. By Fi<^- 140.— Dia- 

 ^ "^ ^ ^ "^ era 111 of the 



this "suppression" is meant the non-appearance of flowerofP^-m- 



an organ which one would expect to aj^pear accord- (.^f"^" jcrass and 

 ing to reasons deduced from comparative morphology, Lando.s.) 

 In some cases an entire -whorl ma}' be suppressed or fail to appear. 

 In other cases there is not a suppression of members, but an increase 

 in the normal number of parts {'"'' dedouhlement "). 



Since Schumann' has applied Schwendener's contact theory to 

 the processes of growth and development in the floral region of 

 the plant the investigations in regard to this subject have been 

 placed upon a firmer foundation, while the play of fancy is to a cer- 

 tain extent checked. The exact history of development, the study 



' Neue UuteisuchuDgen uber deu Bluteuanschluss, Leipzig, Eugelmann, 1890. 



