MORPHOLOGY OF ANGIOSPERMS. 137 



MORPHic or RADIAL, and irregular flowers as zygomorphic. The 

 latter are also spoken of as dorsiventral and usually occur as 

 lateral flowers in an inflorescence, as in Vanilla (Fig. 133), Aco- 

 nitum (Fig. 141) and Lobelia (Figs. 180, i8oa) ;" whereas radial 

 flowers are solitary, as in Sanguinaria (Fig. 148), or terminal 

 as in Geranium (Fig. 155), or they may also be lateral as in 

 Phytolacca (Fig. 139). Dorsiventral flowers either arise as such, 

 as in some of the Leguminosse (Fig. 88), or they may arise as 

 radial flowers and become dorsiventral during the course of devel- 

 opment, as in willow herb (Epilobium). 



In some flowers the floral envelopes are wanting, and the 

 flowers are said to be naked, as in the willows and grasses. 



Anthotaxy.^ — Just as a flower may consist of one or more 

 parts, so a flower-branch may bear more than one flower. The 

 stalk of the individual flowers is called a pedicel, while the main 

 axis, or branch bearing the collection of flowers, is called a 

 PEDUNCLE. The study of the arrangement of flowers on the stem 

 is known as anthotaxy. 



If we compare the flower clusters of morning glory and bind 

 weed (Fig. 174) with those of the poke weed (Fig. 139) we will 

 find that in the former the number of flowers that may be pro- 

 duced is limited because the middle flowers of the group, or those 

 at the apex of the branch, mature-first ; while in the poke weed, 

 on the other hand, the end of the branch has a large number of 

 flower buds, and as these develop others continue to be formed. 

 It is obvious that in the latter case the number of flowers that 

 may be produced is more or less indefinite, and this kind of antho- 

 taxy, or inflorescence, is known as indeterminate or indefinite 

 inflorescence, while in the case of the morning glory, the inflor- 

 escence is said to be determinate or definite. 



The INDETERMINATE or INDEFINITE INFLORESCENCE IS the 



most general and includes the following kinds : In poke weed the 

 individual flowers are of about the same size, and these are ar- 

 ranged along a central axis, or rachis, the inflorescence being 

 known as a raceme (Fig. 139) ; in oat. Yucca and Brayera' the 

 individual flowers are replaced by a cluster of flowers, constitut- 

 ing a compound raceme or panicle (Fig. 150) ; in the cultivated 

 cherry the rachis is somewhat shorter than that in a raceme, and 



