72 



MORPHOLOGY OF THE ANGIOSPERMS 



the remaining flowers or flower. Involucres of this type may be petaloid 

 and simulate a corolla or perianth — Actinotis ( Umbellif erae ) , Phnelea 

 ( Thymelaeaceae ) , Leucademlron and Protea ( Proteaceae ) , Cornus. 



Reduction in flower number has taken place in many genera through- 

 out angiosperms. Examples of reduction to one flower from racemose 

 clusters are seen in Droscra, TiiUpa, Plantago, Cypripcdkim, Moncses, 

 Vicia, Vaccinium, Scutellaria, Gentiana, Monotropa, Ornithogalum; from 

 cymose clusters in Narcissus, Viola, Pofentilla, Silcnc, Daliharda, Rosa, 

 Anemone, Philadelphus, Rubus, Vinca. A solitary flower may represent 

 one surviving member of a raceme, as in Vicia (Fig. 31); of an umbel, 

 as in Xanthosia ( Umbelliferae ) ; and of a head, as in Corynibium (Com- 



1^ ^ 



1 



i 



B 



i 



1 



I 



I 



Fig. 30. Diagrams showing progressive reduction of lateral branclilets of the 

 inflorescences of coryphoid palms. A, all axes more or less shortened; B, ultimate 

 branchlets (pedicels) shortened, flowers sessile; C, flower-bearing branchlets re- 

 duced to hemispherical bases; D, lateral branchlets wholly reduced, the base 

 elongated, flowers borne in a row along main axis. Reduction in flower number 

 continuous from many to three (triads) or two, sometimes sunken in the fleshy 

 main axis. {After Bosch.) 



positae). Each flower of a head may be the surviving flower from one 

 of a compacted cluster of heads, as in Echinops, Oedera (Compositae). 

 Where reduction is to a few-flowered cluster, no satisfactory descriptive 

 term may be applicable, and such phrases as "umbellate cluster" (in 

 Rosaceae) and "contracted cymose cluster" (in Labiatae) are used. 

 The morphological nature of the cluster may be obscure, unless com- 

 parisons are made with inflorescences of related taxa. 



Solitary flowers like that of the quince bush (Cydonia) have been 

 cited as examples of primitive solitary flowers. But the evidence of re- 

 duction through a racemose-umbellate series exists in the related genera, 

 Pyrus, Malus, Chaenomeles. Chaenomeles shows all tlie stages in this 

 reduction, 



