496 PART III. THE CLASSIFICATION OF PLANTS. 



chemilla) the stipules of the sepals form a calyculus or epicalyx: 

 stipules are developed in connexion with the petals of some 

 Sapotacece (Dipholis, Mimusops) ; and in connexion with the 

 stamens of Allium, Ornithogalum, some Zygophyllaceas, etc. 



The Pliyllotaxy of the Flower. The floral leaves, like the foliage- 

 leaves on the stem (see p. 25), are frequently arranged spirally, 

 (e.g. Calycanthus, Anemone, Trollius) when the flower is acyjdic^ 

 The most common divergence is f, but higher divergences also 

 occur, especially in the androecium, when numerous small organs 

 are inserted upon an expanded axis (e.g. Ranunculus). In the 

 spiral or acyclic flower there is either no well-marked distinction 

 of the various series, that is, the members of the calyx, coroVlg,, 

 and andrcecium, are connected by intermediate forms (e.<^Nym- 

 phsea) ; or the various series are sharply defined, each series taking 

 up one or more turns of the spiral. 



In most cases the floral leaves are arranged in whorls, that is, 

 the flowers are cyclic. Cyclic flowers are connected by inter- 

 mediate forms with the acyclic, especially through pentamerous 

 forms. Thus some pentamerons flowers are hemicyclic, that is, 

 some of their floral leaves are arranged spirally, and the others in 

 whorls. Instances of a spiral perianth combined with cyclic sporo- 

 phylls are afforded by those flowers in which the members of the 

 perianth, calyx, or corolla are developed in - succession, and the 

 prefloration is quincuncial (see p. 60) ; the perianth is spiral in 

 the flowers of the Cannabinacese, Chenopodiacea3, and Amarantacese; 

 the calyx is spiral in the flowers of the Bindweed (Calystegia 

 Sepium), the Rose, some Boraginacese (Cerinthe, Echium, etc.), 

 Geraniaceae, Oxalidacese, Linacea3, Caryophyllaceaa, and many other 

 dicotyledonous orders; both calyx and corolla are spiral in Tern- 

 strcemia and Clusia. Though the phyllotaxy is not f in Camellia, 

 the calyx and corolla are spirally arranged. In other cases, the 

 Sorophyljis are spirally arranged, whilst the perianth-leaves are 

 cyclic. For instance, in Magnolia, Ranunculus, and Helleborus, 

 both stamens and carpels are spirally arranged ; and in Delphinium 

 and Aconitum, the stamens only. 



Closely related to the foregoing cases of phyllotaxy occur- 

 ring in fact not only in flowers of closely allied species, but also 

 in flowers of the same species arc certain of the typical forms of 

 cyclic arrangement in which each series (whether perianth, calyx, 

 corolla, or androecium), instead of consisting of five floral leaves, 

 taking up two turns of a spiral with a divergence of -f , consists of 



