xiii FLOWER AND INFLORESCENCES 171 



Hazel, and Sweet Chestnut are arranged in catkins. Both the 

 male and female flowers of the Willow, Poplar, and Birch form 

 catkins. 



EXPT. 162. In either April or May obtain an Arum and examine it. 

 Note 



(i) The yellowish-green spathe which surrounds the spadix. It is 

 longer than the spadix. 



(ii) Cut away the spathe. Notice the inside is, as a rule, full of small 

 flies. The spadix, which is thick and fleshy, is seen within and is 

 generally of a purple colour above the flowers. 



(iii) The female flowers are at the base of the spadix and the male 

 flowers are just above these. There is a ring of undeveloped male 

 flowers just above the fertile male flowers. 



EXPT. 163. Collect a few catkins of the Hazel. They are produced 

 in the months of February and March. Examine one. Note 



(i) The external appearances of the inflorescence. It is pendulous. 



(ii) Remove a single flower with a pin. Observe each flower is 

 connected by a very short stalk or is sessile on the peduncle. Only 

 stamens are found in each flower. 



(iii) The inflorescence is a spike of male flowers. 



Relation between Indefinite Inflorescences. The 



raceme only differs from a spike in having pedicels which sepa- 

 rate the flowers, so that they make a better show and are more 

 likely to be seen by insects than the sessile flowers on a spike. 



The panicle, which is a compound raceme, generally bears 

 only small flowers, and the arrangement of these on the ends 

 of small stalks causes them to be seen for a great distance. It 

 differs from both the spike and raceme ; from the former in 

 possessing stalks, and from the latter in having these branched. 



The corymb differs from the raceme in having the pedicels of 

 unequal length, and in the flowers being all brought to the same 

 level. Thus, a more or less flat surface, upon which insects love 

 to rest and collect honey, is formed. 



In the head the same result is obtained by the flowers being 

 crowded together on a flat receptacle, an arrangement which 

 also makes them very conspicuous. 



Both the catkin and the spadix are spikes ; the former is a 

 catkin of male flowers, while the latter bears both male and 

 female flowers. The catkins are produced before the leaves, 

 and by their pendulous position aid in the distribution of the 

 pollen by the wind. 



