748 THE AMERICA.X XA JL RAUST. [X'ol. XXXVIII. 



Mitotic phenomena in the Siphonales is known to us only 

 through the investigations of Fairchild (94) on Valonia. He 

 found that nuclei in the same individual may divide directly or 

 indirectly. The first process is one of smipie fission, the latter 

 takes place with the formation of an intranuclear spindle. 

 Studies in sporogenesis and gametogenesis are very much to 

 be desired in the Siphonales that we may understand the 

 behavior of the nuclei at these periods. The author's recent 

 studies of oogenesis in Vaucheria (Davis, : 04^) have shown an 

 interesting process of nuclear degeneration similar to that in the 

 Saprolegniales and Peronosporales, and suggests some very inter- 

 esting lines of investigation. 



The protoplasmic structure in the hyphai of the larger fila- 

 mentous Phycomycetes, especially the Saprolegniales and Perono- 

 sporales, is undoubtedly much the same as in the Siphonales. 

 But the absence of chlorophyll and the greater delicacy of the 

 filaments makes it more difficult to recognize the different 

 regions of the protoplasm. There is an outer plasma membrane 

 inside of which the granular material slowly moves in proto- 

 plasmic currents that may sometimes be obserx ed in rapidly 

 growing tips. Delicate strands which are the paths of stream- 

 ing currents are beautifully shown in developing sporangia of 

 the molds and the oogonia of the Saprolegniales and Perono- 

 sporales. The nuclei are undoubtedly carried by the protoplas- 



le plasm(xlium of the M)xomycete. These 

 ) well known to need description here. We 



them as they help to break down an old 

 enocyte is a compound structure composed of 

 ^'IMcsented by the nuclei, which cooperate to 

 "le. The plasmodium and the protoplasmic 

 cllulose tubes of the Siphonales and Phycomy- 



1 essentials of structure and mode of growth, 

 wth of the Plasmodium, as is also true of the 



