SPORE LIBERATION 



its release only in dty weather. In Taxus, Thuja, Cupressus, and ^uniperus, 

 the pollen is not winged. In ^uniperus the expanded ends of the cone- 

 scales interlock closely in damp weather, separating again in dry air and 

 allowing pollen to be blown out. 



ANGIOSPERMS 



Details of flowering-plant pollination mechanisms are given by Mari- 

 laun (1895), Knuth {1906), Erdtman (1943, 1952, 1957), Wodehouse 

 (1945) and others. 



Fig. 5. — Anthesis of false oat-grass {Arrhenatherum elatius): (i) closed anther; 

 (2) open anther; (3) spikelets on a calm day; and (4) spikelets in a wind. (Repro- 

 duced from Marilaun's: Natural History of Plants, by permission of Messrs. 

 Blackie & Son, Limited.) 



(i) Grasses, rushes, sedges and their allies. The Gramineae, Cyperaceae, 

 Typhaceae, and Juncaceae are typically wind-pollinated. From the raised 

 inflorescences of grasses, the anthers are extruded on long filaments to 

 which they are so lightly attached that they vibrate in the slightest wind. 

 Often, as in Arrhenatherum, the end of each pollen-sac bends up (Fig. 5), 

 forming a spoon into which pollen is shed from a slit, and where it ac- 

 cumulates until blown away by the wind. Either damp or ver>- dry weather 



41 



