I9071 



CALDWELL— MICROCYCAS CALOCOMA 



129 



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become entirely free from one another before the ciliated band is 

 formed. In Zamia Webber points out that the ciliated band is 

 formed before the mother cells become separate, and describes one 

 case in which he observed two sperms swimming while yet attached 

 to each other. 



In this manner sixteen sperms are formed in each pollen tube 

 (figs, 28, 2g), In those pollen tubes in which nine or ten (or possibly 





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Fig. 7. — A young plant of the t^^pe usually found in exposed regions. The crown 

 of such plants suggests that of Cycas revoluta. 



more 



sperms is formed, but no case was observed in which there were 



more 



When 



tube grows toward the female gametophyte {fig. 26). In one case 

 the entire mass of sperms was formed within the thicker portion of the 

 inline, at the point where the fx)llen tube began to develop from the 

 microspore {fig. 2p). Whether in this particular case there had been 

 an upward growth of the pollen tube could not be determined. Usu 



