490 PAET III. THE CLASSIFICATION OF PLANTS. 



Boraginaceae the bract often undergoes displacement, so that it 

 appears to be inserted laterally o-pon the axillary branch ; on the 

 other hand, it sometimes happens that the axillary branch is 

 adherent to the main shoot for some distance. 



The flowers of an inflorescence are either sessile or stalked, the 

 stalk being termed a pedicel. 



In accordance with the principles of branching laid down on 

 p. 33, the different forms of inflorescences may be classified as 

 follows : 



A. Racemose Inflorescences consist of a main axis (rhachis, peduncle), 

 bearing a number of lateral branches developed in acropetal (or centripetal) 

 succession, constituting a monopodial branch-system. The lateral branches do 

 not usually grow longer than that portion of the main axis which lies above 

 their points of origin. If the lateral shoots of the first order terminate in a 

 flower without again branching, the inflorescence is said to be simple ; but if 

 they branch, it is compound. 



These inflorescences are also termed indefinite, not because the apical growth 

 of the main axis or of its branches is unlimited, but because, owing to the 

 acropetal succession in the development of the flowers, the growth of branches 

 of a high order is arrested, by the development of a terminal flower, earlier than 

 tbat of branches of a lower order : for instance, the growth of the secondary 

 branches is arrested before that of the main axis, that of the tertiary branches 

 before that of the secondary branches, and so so. 



I. Simple racemose inflorescences : 



(a) With an elongated main axis : the lateral shoots spring from the axis at 

 some distance from each other. The three following forms may be distin- 

 guished : 



(1) The spike, in which the lateral branches are flowers which are sessile on 

 the main axis, or have very short pedicels (Fig. 309 A] ; e.g. the inflorescence 

 of the Plantain (Plantago). The small spikes of the Glumales are termed 

 spikdets. 



(2) The spadix, which differs from the spike only in having a thick and fleshy 

 axis ; a large bract forming a sheath, called a spathe, commonly grows at the 

 base of the inflorescence and envelopes it more or less ; e.g. Arum and 

 Kichardia. 



(3) The raceme, in which the lateral branches are flowers with pedicels of 

 nearly equal length, e.g. the Cruciferse, as the Eadish, Cabbage, etc. ; in these 

 the bracts of the individual flowers are not developed; also Berberis and others. 



(/3) With a short main axis ; the lateral branches are set closely together on 

 the short or flattened main axis. 



(4) The capitulum (head) in which the short main axis is conical or disc- 

 shaped or even hollowed out, and is closely covered with lateral branches in 

 the form of sessile flowers (Fig. 309 Z>), e.g. the Compositae, as Dandelion, 

 Sunflower; also the Scabious. The bracts (paleae) of the individual flowers 

 (Fig. 309 Dp) are sometimes wanting ; but the whole head is surrounded at the 



