FLOWERS AND THEIR WORK. 231 



met with, noting that plants with inflorescences of this kind are found 

 in many different Orders e.g. Cruciferae (Candytuft, etc.), Rosaceae 

 (Cherry, Rowan, Meadowsweet, Hawthorn, etc. ),Leguminosae (Clovers, 

 Lotus, etc.), Umbellifers, Ivy, Dogwood, Elder, Valerians, Dipsaceae, 

 Sheep's-bit, Compositae, eto. 



It seems probable that all cymose inflorescences have been derived 

 from racemose ones by a shortening of the main axis and a delay in 

 the development of the lateral branches, to which the main power of 

 growth is at the same time transferred. The cymose inflorescence 

 is certainly an advance upon the racemose type, for in the former 

 new flowers continually appear on the exposed surface of the inflores- 

 cence, while the fruits ripen securely buried among the older parts 

 of the mass of branches. The tendency in racemes, on the other hand, 

 is to simultaneous flowering, such as is exhibited more or less 

 perfectly by so many umbels and capitula and especially by corymbs. 

 In such cases there is an ever-present danger that the short period 

 of flowering may occur at a time when the conditions are not suitable 

 for the production of fertile 



Racemes such as those of 

 the Wallflower, in which the 

 lower flowers may open months 

 before the apex of the raceme 

 ceases flowering, do not incur 

 this danger, but the exposed 

 position of the young succu- 

 lent fruits is an obvious dis- 

 advantage here and in other 

 Crucif ers also. If the growing 

 point of a young raceme is 

 destroyed, the power of pro- 

 ducing flowers may be tem- Fig- 80. A Compound Umbel. 

 porarily lost, whereas the 



destruction of the apex of a cyme involves the loss of a single flower 

 only, and the lateral axes continue their growth with even greater 

 vigour than before. 



Compound inflorescences are those in which the lateral branches 

 are again branched in the same way as the parent axis. The com- 

 monest kinds are (1) Panicle (raceme of racemes or spikes), common 

 in Grasses ; (2) Compound spike (a spike of spikes), in some 

 Grasses, e.g. Wheat ; (3) Compound umbel, much commoner than 

 the simple umbel (most Umbelliferae, Fig. 80). 



In many cases mixed inflorescences occur as, for example, 

 racemes of spikes, capitulums, or cymes, spikes of capitulums, etc. 

 It must, however, be borne in mind that there are only three main 

 types of inflorescence, and these are (1) the raceme, with its reduction 

 derivatives grouped around the generalised panicle type ; (2) the 

 biparous cyme ; (3) the uniparous cyme. " Mixed " inflorescences 

 arise owing to the fact that reduction or alteration has unequally 

 affected the different parts of the primitive panicled inflorescence. 



