THE INFLORESCENCE 71 



some examples of these has been misinterpreted, because of complexities 

 of nodal structure. Variations in pedicel length and in orientation of 

 flowers produce forms of inflorescences difficult to place in the usual 

 categories. In all the determinate types, branching may continue suc- 

 cessively, as in the first cluster, and large, compound, cymose in- 

 florescences be built up. In these clusters, the ultimate three-flower unit 

 is often called a cymuJe. This term is applied also to the few units sur- 

 viving in a small cluster reduced from a large one, as in the Betulaceae. 



The term panicle is applied to large, branched, racemose inflores- 

 cences, but it is more commonly used for large, loose clusters of any 

 type, determinate, indeterminate, or mixed. The inflorescence of the 

 lilac, Sijringa, is racemose, but all its branchlets have a terminal flower, 

 and those that have only three flowers form a typical cyme. The large 

 inflorescences of many grasses — for example, the rice, Oryza — are 

 cymose in major, racemose in minor branching. In large inflorescences, 

 such as those of many rosaceous genera — Crataegus and Ruhus, for 

 example — the order of development may be irregular and inconstant. 

 The umbel may be determinate or indeterminate. The importance of 

 sequence in development has been overemphasized. 



Some, perhaps many, of the apparently simple inflorescences — cer- 

 tain types of monochasia, even some racemes — are not morphologically 

 simple but represent reduced branched types, as is shown by anatomy 

 and critical comparative studies. Some dichasia become simple by the 

 abortion of the terminal flower; the branching then appears dichoto- 

 mous; compound dichasial inflorescences reduced in this way have been 

 called dichotomous. 



Branched inflorescences of any type are called compound, as con- 

 trasted with simple, but this is, morphologically, a valueless distinction. 

 Many apparently simple clusters have been derived from branched 

 ones by reduction, but the origin is more or less obscure. For example, 

 the apparently simple "raceme" of Claijfonia is not simple but highly 

 complex in nature. The raceme and the dichasium are commonly called 

 the basic simple types, but die dichasium is a branched, not simple, 

 inflorescence. 



Reduced Inflorescences 



In the evolutionary modification of inflorescences, reduction and con- 

 densation have played prominent parts (Fig. 30). Reduction is pri- 

 marily in flower number, but the stem system is commonly also in- 

 volved; internodes are shortened or suppressed, and, in reduction to 

 one flower, nearly all the stem system may be lost. The bracts of the 

 reduced stem system may similarly be greatly reduced, but they may 

 be retained where the internodes are lost and form an involucre about 



