76 MORPHOLOGY, OB COMPAEATIVE ANATOMY. 



a single bracteole, while in many Dicotyledons there are two ; in the 

 former case the anterior surface of the bracteole is directed towards the 

 primary axis from which the flower is produced, in the latter the two 

 bracteoles are lateral or oblique to the axis. 



As a general rule, all ramifications of inflorescence arise in 

 the axils of bracts ; but the bracts are sometimes regularly abor- 

 tive, as in the Cruciferse. On the other hand, we sometimes find 

 the lower part of the inflorescence crowded with bracts with empty 

 axils. 



Spathe. In many plants the bract subtending the whole inflo- 

 rescence or its principal branches is large, and forms a kind of 

 sheath, called a spathe. Sometimes this surrounds only one flower, 

 as in some Daffodils, &c., where it is of membranous texture ; the 

 membranous spathe of the Onion and its allies encloses a dense 

 inflorescence ; in the Araceae (fig. 133) it is still more developed, 

 and sometimes of petaloid structure, as in the so-called Trumpet- 

 lily (Richardia cethwpica\ w r here it encloses the club-like inflores- 

 cence; while in the Palms (fig. 134) it assumes enormous dimen- 

 sions and a leaf-like or even fibrous texture, forming a sheath to a 

 large and greatly ramified inflorescence. 



Involucre. In other cases, several bracts are collected together, 

 forming a whorl or densely packed spire, called an involucre. The 

 Umbelliferae have frequently verticillate involucres at the base of 

 the umbels, and sometimes secondary whorls or involucels at the 

 base of the secondary umbels (fig. 140). In the Composite also, 

 where the flowers are crowded on a common receptacle, the bracts 

 form an involucre (figs. 141-146) ; smaller scale-like bracts occur- 

 ring among the florets of these eapitula are called palece (figs. 145 

 & 146). Other examples of involucre are furnished by the cu pules 

 of the Oak, Beech, Filbert, &c., wherein the bracts are united or 

 not disconnected at the base ; also by the outer glumes or scales of 

 the spikelets of Grasses. 



Forms of Inflorescence. The different forms of the Inflo- 

 rescence are divisible into two classes : 1, the indefinite, where 

 the terminal bud of the main or primary axis does not form a 

 flower, the flowers being borne on secondary lateral branches, 

 which are as a rule smaller and weaker than the main axis ; and, 2, 

 the definite, where the primary axes either bear terminal flower- 

 buds, while the succeeding flowers spring from secondary axillary 

 branches produced lower down, and subsequently to the terminal 

 bud, or branch in a forked manner without producing a flower 

 in the centre of the fork. The secondary branches are here as 

 strong or stronger than the main axis. The forking is not neces- 



