DISPERSION OF POLLEN BY THE WIND. 



143 



extremity becomes pendulous, and the anther hangs from it and encounters no 

 obstacle to movements such as are required to shake out the pollen. 



As in the case of Grasses and Sedges, so also in Hemp and Hops (Cannabis, 

 Humulus), and in numerous species of Sorrel and Meadow-rue {e.g. Riimex alinnus 

 and R. scutatus, Thalictrum alpinum, T. faetidum, T. minus) the pollen-dust is 

 shaken out of anthers which are pendulous at the ends of delicate filaments; only, 



Fig. 232.— The Elm (Uknus campestris). 

 1 With flowers. 2 With fruits. 



in these plants not glumes but small perianth-leaves form the protective envelope 

 round the anthers before they open. Moreover, in Hemp and Hops, and the above- 

 mentioned species of Meadow-rue, the anther-lobes do not burst wide open when 

 they dehisce, but exhibit parallel slits which are at first so narrow that the pollen 

 can only shake out little by little. Plantains (Plantago) also have their pollen 

 shaken out of the anthers, which are borne on long filaments, by the wind. The 

 filaments are tucked in so long as the flower is in bud, but when the petals unfold 

 the filaments straighten out and project beyond the floral spike. The versatile 



