80 THE FLOWERING PLANT. 



cyme may also be three-rayed, four-rayed, &c, when three, four, 

 &c, lateral branches overtop the main axis. (2.) The nature 

 of a pseudaxis or sympodium has already been fully explained 

 (pp. 24, 48). The pseudaxis may either be formed by branches 

 developed on either side alternately, when it is scorpioid, or by 

 branches belonging to one side only, when it is helicoid. The 

 vegetative shoots of elm, &c., and flowering shoots of deadly 

 nightshade are instances of the former, while forget-me-not 

 illustrates the latter case, where the pseudaxis naturally curls 

 round in a spiral way (fig. 36). 



Compound cymes are distinguished by the fact that branches 

 of secondary or higher order themselves bear cymes instead of 

 terminating in flowers. Elder is a common example. A com- 

 pact cyme is termed a fascicle, and if so condensed as to look like 

 a capitulum, it is a glomerulus. 



Mixed inflorescences, which combine more or less the racemose 

 and cymose types, are not uncommon. As might be expected, 

 flower clusters of this nature are usually compound. Compara- 

 tively few special names have been given to these cases, since it 

 is easier to describe the general and partial ways of branching 

 separately. The heads of Composites, for example, are often 

 arranged in a cymose manner. Panicles are frequently mixed, 

 and the general name thyrsus has been given to elongated com- 

 pact forms in which the primary branching is racemose and the 

 secondary cymose, as in the flowering shoots of lilac and horse- 

 chestnut. The verticillaster is a variety of thyrsus found in some 

 plants, such as dead nettles, where the leaves are opposite and 

 decussate. At first sight there appears to be a circlet of flowers 

 at each node, the uppermost circles being youngest, so that the 

 general arrangement is racemose or indefinite. Careful exami- 

 nation shows, however, that each apparent circlet is in reality 

 composed of two very short cymose flower clusters in the axils of 

 the opposite leaves. 



The flower, as a whole, generally displays a certain symmetry, 

 as seen on ground-plan. It is usually either radially symmetrical 

 or bilaterally symmetrical (cf. p. 5 2). 1 In the latter case the median 

 or antero-posterior plane is in most cases the one which divides it 

 into similar halves. 



Lastly, a flower may be asymmetrical, when it is not divisible 

 by any plane into similar halves. Flowers coming under the 

 second and third cases may conveniently be called irregular. In 

 determining the irregularity or otherwise of a flower, calyx and 



1 Radially symmetrical flowers are also termed regular, poly symmetrical, or 

 actinomorphic, and bilaterally symmetrical ones zygomorphic or monosym- 

 metricaL 



