LESSONS ON PL AN T FAMILIES. 249 



Umbel; the main axis is shortened, and the stalked flowers appear to 



form terminal clusters or whorls, as in the parsley, carrot, parsnip, 



etc. 

 Head, or capitulum; the main axis is shortened and broadened, and 



bears sessile flowers, as in the sunflower, button-bush, etc. 

 Panicle; when the raceme has the lateral axes branched it forms a 



panicle, as in the oat. When the panicle is flattened it forms a 



corymb. 



Sympodial branching or cymose branching. The branches, or lateral 

 axes, grow more vigorously than the main axis, and form for the 

 ' time false axes (form cymes). 



1. Monochasium; only one lateral branch is produced from each rela- 

 tive or false axis. 



Helicoid cyme; when the successive lateral branches always ariseon 

 the same side of the false axis, as in flower clusters of the forget- 

 me-not. 



Scorpioid cyme; when the lateral branches arise alternately on op- 

 posite sides of the false axis. 



2. Dichasium; each relative, or false, axis produces two branches* 

 often forming a false dichotomy. Examples in shoots are found in 

 the lilac, where the shoot appears to have a dichotomous branch- 

 ing, though it is a false dichotomy. 



Forking cyme; flower cluster of chickweed. 

 j. Pleiochasium; each relative, or false, axis produces more than two 



branches. 



485. The fruit. The fruit of the angiosperms varies greatly, and often is 

 greatly complicated. When the gynoecium is apocarpous (that is when the 

 carpels are from the first distinct] the ripe carpels are separate, and each is a 

 fruit. In the syncarpous gyncecium (when the carpels are united) the fruit is 

 more complicated, and still more so when other parts of the flower than 

 the gynoecium remain united with it in the fruit. 



Pericarp; this is the part of the fruit which envelops the seed, and may 

 consist of the carpels alone, or of the carpels and the adherent part of 

 the receptacle, or calyx ; it forms the wall of the fruit. 

 Endocarp and exocarp. If the pericarp shows two different layers, or 

 zones, of tissue, the outer is the exocarp, and the inner the endocarp, 

 as in the cherry, peach, etc. 



Mesocarp; where there is an intermediate zone it is the mesocarp. 

 I. CAPSULE (dry fruits). The capsule has a dry pericarp which opens 

 (dehisces) at maturity. When the capsule is syncarpous the carpels may 

 separate along the line of their union with each other longitudinally 

 (septicidal dehiscence}; or each carpel may split down the middle line 



