ELEMENTARY BOTANY. XI 



always centripetal. Both inflorescences may be combined on one plant, for it often 

 happens that the main branches of an inflorescence are centripetal, whilst the flowers 

 on the lateral branches are centrifugal ; or vice versd. 

 74. An Inflorescence is 

 a Spike, or spicate, when the flowers are sessile along a simple undivided axis or 

 rhachis. 



a Raceme, or racemose, when the flowers are borne on pedicels along a single un- 

 divided axis or rhachis. 



& Panicle, or paniculate, when the axis is divided into branches bearing two or 

 more flowers. 



a Mead, or capitate, when several sessile or nearly sessile flowers are collected 

 into a compact head-like cluster. The short, flat, convex or conical axis on which the 

 flowers are seated, is called the receptacle, a term also used for the torus of a single 

 flower (135). The very compact flower-heads of Composite are often termed com- 

 pound flowers. 

 , an Umbel, or umbellate, when several branches or pedicels appear to start from 

 the same point and are nearly of the same length. It' differs from the head, like the 

 raceme from the spike, in that the flowers are not sessile. An umbel is said to be 

 simple, when each of its branches or rays bears a single flower ; compound, when each 

 ray bears a partial umbel or umbellule. 



a Corymb, or corymbose, when the branches and pedicels, although starting from 

 different points, all attain the same level, the lower ones being much longer than the 

 u Pper. It is aflat-topped or fastigiate panicle. 



a Cyme, or cymose, when branched and centrifugal. It is a centrifugal panicle, 

 and is often corymbose. The central flower opens first. The lateral branches succes- 

 sively developed are usually forked or opposite (dichotomous or trichotomous), but 

 sometimes after the first forking the branches are no longer divided, but produce a suc- 

 cession of pedicels on their upper side forming apparently unilateral centripetal ra- 

 cemes ; whereas if attentively examined, it will be found that each pedicel is at first 

 wminal, but becomes lateral by the development of one outer branch only, imnie- 

 thet U i ndei " th ° P ediceL Such branches, when in bud, are generally rolled back at 



°*ttI ^ le * ad °^ a 8Cor pi° n > and arc thence called scorpioid. 



a Thyrsus, or thyrsoid, when cymes, usually opposite, are arranged in a narrow 

 Pyramidal panicle. 



t • ' lllere are numerous cases where inflorescences are intermediate between some 



°, tlle above, and are called by different botanists by one or the other name, ac- 



wh i 88 tUey are g uided b y apparent or by theoretical similarity. A spike-like panicle, 



e the . ax is is divided into very short branches forming a cylindrical compact mflo- 

 ™scence, is called sometimes a spike, sometimes a panicle. If the flowers are in dis- 

 orl 8ter8 alon S a sim ple axis, the inflorescence is described as an interrupted spike 

 wh i G ' accordin g as the flowers are nearly sessile or distinctly pedicellate ; although 

 bu . en c, °sely examined the flowers will be found to be inserted not on the main axis, 



7fi 0na , ver y sh °rt branch, thus, strictly speaking, constituting a panicle, 

 the ostein* (amenta) of Amentacea, the spadices of several Monocotyledons, 



ear* and spikelets of Grasses are forms of the spike, 

 uncle r ? cts are generally placed singly under each branch of the inflorescence, and 

 under !? J** 1 * 061 5 bracteoles are usually two, one on each side, on the pedicel or close 

 alon/ti u ° Wer ' or even u P on the cal y x itself i but bract8 are als0 fre( l uentl y scattered 

 bract* ,i u " Ches without axillary pedicels; and when the differences between the 



78 m bracteoles ar e trifling or immateral, they are usually all called bracts, 

 nation k , these brac ts appear to proceed from the same point, they will, on exami- 

 bracf l • und *° b* reall v either one bract and two stipules, or one bract with two 

 win „ i, ? lt8 axil - When two bracts appear to proceed from the same point, they 

 of the "fl 7 be found to be the stipules of an undeveloped bract, unless the branches 



79 ^? orescen ce are opposite, when the bracts will of course be opposite also. 

 Pear '» i , 8ever al bracts are collected in a whorl, or are so close together as to ap- 

 collerti i ' 0r are c,08eI Y imbricated round the base of a head or umbel, they are 



Uvel y c a«ed an Involucre. The bracts composing an involucre are described 



