502 



CATKIN TRIBE; POPLAR, HAZEL. 



FIG. 180. CATKINS OF BIKCH. 



When the stamineous flowers are distinct, they are generally 



destitute of perianth, but 

 the stamens spring from a 

 sort of scaly disk ; they 

 are usually clustered to- 

 gether, either on a long 

 stalk, forming a catkin, or 

 on a sort of head. The 

 pistilline flowers com- 

 monly possess a perianth 

 in one whorl ; they are 

 sometimes solitary, and 

 sometimes arranged on a 

 catkin. "What may be 

 regarded as the most cha- 

 racteristic structure of the 

 group, is seen in thePojt?- 

 lar and Willow. In these, 

 the stamineous flowers 

 are on one plant, and the pistilline on another ; and both are 

 arranged in catkins. Each of the former consists of a little 

 bract, protecting one or many stamens ; and each of the latter 

 consists of a nearly similar bract, on which is set a one-celled 

 ovarium containing many ovules. The fruit opens by two 

 valves, which discharge a multitude of small seeds, covered with 

 fine hair or wool, like the seeds of the Cotton plant. The 

 Willow has no trace of a real calyx ; but the Poplar has a 

 sort of membranous cup, which may be considered as the rudi- 

 ment of one. 



677. A nearly similar structure is seen in the common Hazel; 

 in which, however, the two kinds of flowers are arranged on the 

 same tree ; and the fruit more resembles that of the Oak. The 

 stamineous flowers grow in catkins ; but the pistilline flowers 

 grow near these, clustered together within a scaly envelope, which 

 looks like a little bud. At the time when the stamens are shed- 

 ding their pollen, the clusters will be recognised by the little red 

 threads protruding from their points, which are the stigmas. 



