70 



INFLORESCENCE. 



194. 192 



192, Ileliantlms grosse-serratus. 1, involucre ; r, rays, or ligulate flowers ; 193, one of tho 

 disk flowers with its chaff-scale (bract). 194, Acorn of moss-cup oak (Q. macrophylla). 195, 

 Poa pratensis ; f, spikelet entire, g, glumes, separated; c, a flower separated, displaying the two 

 pak-ae, 3 stamens, and 2 styles. 



339. In the grasses the bracts subsist under the general name of 

 chaff. The bracts situated at the base of a spikelet of flowers, are 

 called the glumes, corresponding to the involucre. Those situated at 

 the base of each separate flower are palccc, answering to the calyx or 

 corolla. The pieces of which each calyx is composed (generally two) 

 are called valves or pales. 



340. Other examples of the involucre are seen in the cup of the 

 acorn, the burr of the chestnut, beech, etc. 



341. The forms of inflorescence are exceedingly various, but may 

 all be referred to two classes, as already indicated ; the axillary, in 

 which all the flowers arise from axillary buds, the terminal, in which all 

 the flower-buds are terminal. 



342. Axillary inflorescence is called indefinite, because the axis, 

 being terminated by a leaf-bud, continues to grow on indefinitely, de- 

 veloping bracts with their axillary flowers as it grows. It is also called 

 centripetal, because in the order of time the blossoming commences 

 with the circumference, and proceeds towards the centre in case of a 

 level topped cluster, as the hawthorn, or with the base, and proceeds 

 towards the summit in case of the lengthened cluster, as the mustard. 



The student will readily perceive that the circumference of a depressed 

 (flattened) inflorescence corresponds to the base of a lengthened one; 

 and also that the centre of the former answers to the summit of the 

 latter. For when the axis or rachis is lengthened, it is the centre which 

 bears it along with it at its apex, leaving the circumference at the base. 



343. Terminal inflorescence, on the other hand, is definite, im- 

 plying that the growth of the axis as well as of each branch is definitely 

 arrested and cut short by a flower. It is also centrifugal, because the 



