140 THE LOWER FUNGI— PHYCOMYCETES 



They are rigid in habit, usually unbranched, and lack septa other 

 than those cutting off the sexual organs and sporangia. 



Except in the species, M. macrandra Lag., the oogonia and 

 antheridia are borne together on the same hypha. In fact in 

 certain species the antheridium is borne on the oogonium. It 

 differs from the oogonium in size and shape. The oogonium is 

 a rounded to more or less elongate cell tapering above to a defi- 

 nite beak. Before fertilization it ruptures at the apex, an open 

 mouth resulting through which a portion of the contents is 

 expelled by the violence of the discharge. The remainder of 

 its protoplasm then contracts to form a definite oosphere. The 

 spermatozoids escape from the antheridium through a terminal 

 opening and are uniciliate. They swim about, come to rest on 

 the unfertilized oogonium, crawl over its wall with an amoeboid 

 movement, and find their way into its mouth. A single sperma- 

 tozoid effects fertilization, sinking slowly into the substance of 

 the oosphere. In some of the species the fertilized oosphere 

 pushes through the mouth of the oogonium and rounds up 

 outside before assuming the thick wall which marks its transfor- 

 mation into the oospore. In other species it matures within the 

 oogonium. Germination of the oospore occurs apparently in all 

 cases by a germ tube. 



Accounts presented by different workers on the group are 

 not in agreement with respect to the character of the swarm- 

 sporangia and swarmspores. In some of the species large clavate 

 organs resembling the sporangia of Saprolegyiia occur. In 

 these are formed uniciliate cells, which Lagerheim regards as 

 swarmspores. Thaxter's studies indicated that these clavate 

 cells are merely abnormally large antheridia, and he states 

 that intermediate sizes exist between them and the normal 

 smaller type. He says that the sporangia correspond in size 

 and form with the oogonia, and form biciliate swarmspores. 

 Following the appearance of Thaxter's paper Lagerheim founded 

 the genus Diblepharis to include the species in which Thaxter 

 had reported biciliate swarmspores, and retained in Monoblc- 

 -pharis the species in which he believed the swarmspores to be 

 uniciliate. Later Thaxter (1903) reported the biciliate condition 

 in one of Lagerheim's own species. Apparently other workers 

 have never observed biciliate swarmspores, and recently Laibach 

 1927) suggests that the biciliate cells observed by Thaxter were 

 the swarmspores of some parasite which had attacked the 



