hi] racemes : spikes 27 



in detail in the structure of these inflorescences. Those 

 of the Willows and Poplars are the simplest and most 

 typical ; but those of the Alder and Birch, for instance, 

 contain more than one flower in the axils of the bracts, 

 and are really catkin-like spikes composed of small groups 

 of flowers on the one axis. 



The growing apex of some racemes or spikes de- 

 velopes leaves which bear no flowers in their axils, and 

 goes on elongating long after the flowering e.g. Mezereon 

 (Fig. 70), Sea Buckthorn (Fig. 71), Melaleuca, Calliste- 

 mon, Ananassa, &c., and something similar occurs in the 

 case of many Conifers, e.g. the staminate inflorescences of 

 the Pines (Fig. 50) ; but it is evident that these cases link 

 up with those where the presence of flowers in the axils 

 of leaves on foliage-shoots often deters us from calling 

 such shoots spikes, racemes, &c. In Muscari comosum 

 the raceme becomes sterile at its summit, by the ex- 

 haustion and atrophy of the flowers. 



In Genista tinctoria the raceme is interrupted, inter- 

 calated bracts without pedicels in their axils appearing 

 between the flowers. 



The student should notice that in all the simple forms 

 so far described three chief points are in question, viz. the 

 shape of the whole inflorescence, the relations of position 

 between the primary and secondary axes, and the relative 

 eloncjation of these axes. 



The shape is of less importance than the relations of 

 position and elongation, and the student should carefully 

 exercise himself in determining various types of inflores- 

 cence in view of these points. In the field it is of course 

 impossible to make out the facts of development directly, 

 and recourse has to be had to the relative sizes and 

 positions of the buds, bracts, &c. If in an inflorescence 

 which looks like a raceme, for instance, the pedicels do 



