OKDER MONOBLEPHARIDALES 



89 



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Fig. 28. Monoblepharidales, Family Monoblepharidaceae, M onoblepharis poly- 

 morpha Cornu. (A) Zoospore. (B-E) Zoosporangia. (F) Fertilization of oogone. (G) 

 Exogenous oospore. (After Sparrow: Ann. Botany, 47(187) :517-542.) 



antherid is usually 4-7, but in M. insignis Thaxter there may be up to 

 24-32. They are posteriorly uniflagellate and swim to the oogone or creep 

 along its surface in a jerky manner as the flagellum waves. The oogones 

 become uninucleate according to Laibach (1927) before the basal septum 

 is formed. They are pyriform or ovoid and when ready for fertilization 

 become open at or near the apex, sometimes at the top of a short broad 

 neck. The protoplasmic contents round up into a more or less spherical 

 egg near the base of the oogone or close to its opening. Upon entry of the 

 sperm into the egg the flagellum of the former disappears and the fertil- 

 ized egg remains in the oogone and forms a thick wall (endogenous 

 oospore) or creeps out through the oogonial opening and encysts exter- 

 nally (exogenous oospore), in some cases then falling ofT. Rarely both 

 modes of oospore formation may occur in the same species, e.g., M. 

 macrandra. The two sex nuclei do not unite in the oospore until shortly 

 before its germination by a slender germ tube. (Figs. 27, 28.) 



Monohlepharella was distinguished as a separate genus by Sparrow 



