CYCADALES 



141 



It is generally accepted that the cycads are wind-pollinated. 

 Pearson (47), however, observed insects dusted with the pollen of 

 Encephalartos villosus, and believes it is probable that they effect 



Figs. 155-159. — Dioon edule'; the germination of the microspore; fig. 155, the 

 nucleus in early prophase o£ the first mitosis, exine and inline sharply differentiated 

 (August 14, 1905); fig. 156, the shedding stage (September 1906); fig. 15 7, 'beginning 

 of the pollen tube; /, tube nucleus; g, generative cell; p, prothallial cell; fig. 158, 

 the generative cell divided (October 21, 1907), giving rise to stalk cell (j) and bodv 

 cell (6), no blepharoplasts visible; fig. 159, later stage (November 20, 1906), the body 

 cell much elongated and the blepharoplasts with very conspicuous radiations; figs. 

 155-157, Xi,26o; fig. 158, XijOoo; fig. 159, X630. — After Chamberlain (63). 



pollination. In Dioon edule (63), when the pollen is shed, a large 

 pollination drop oozes from the micropyle, just as in gymnosperms 

 which are known to be wind-pollinated, and in this case, also, insects 

 dusted with pollen were found in "the staminate con.es, but there was 

 nothing further to indicate that pollination was being effected through 



