250 BULLETIN 94. 



fission results in the formation of two zoospores which are oval in 

 form with the ciliutn attached directly at the smaller end. 



This peculiarity in the development of the zoospores is one 

 which has not heretofore been recorded except in a preliminary 

 paper by the writer. 15 The species was at that time studied along 

 with the seedling fungus, A. debaryanus (Hesse), and as this is 

 reported as occurring also on fern prothallia ( Todea africana} the 

 species now under discussion was then supposed to be the same, 

 and to this species it was doubtfully referred. But the develop- 

 ment of the conidia is very different from that described for any 

 other species of this genus resembling that of Phytophthora as 

 stated above. 



It cannot therefore at the present time be said with certainty 

 that the zoospore formation in Artotrogus debaryanus is the same 

 as that found for A. intermedius, though what evidence we al- 

 ready have on the subject might be interpreted to support that 

 view of the case. 



Where the soil is kept very damp and the air of the house is 

 quite humid the prothallia are apt to be overrun by certain algae 

 which choke the prothallia, shut out the air and light, prevent 

 their proper development and frequently cause them to be com- 

 pletely sterile. Many of the prothallia are thus killed, sometimes 

 entire beds or pots of them. A very common alga which I have 

 several times observed is a variety of Hormiscia flacdda (Kuetz.) 

 Lagerh. Species of Oscillatoria are also frequently present and 

 produce a like injury. 



If the pots or vessels in which the prothallia are grown are 

 rested on sphagnum a layer of which can be placed in the bottom 

 of the wardian case, and after the young prothallia have started, 

 all of the watering be applied through this, the prothallia will do 

 much better than if surface watering is practiced and far better 

 than where the pots are rested in a vessel partly full of water. 

 The air of the wardian case or of the house should not be kept too 



damp. 



NOTE ON THE GENUS ARTOTROGUS. 



Hesse who first described Artotrogus debaryanus 16 (Pythium de- 



15 Preliminary note on the swarm spores of Pythium and Ceratiomyxa, 

 Bot. Gaz. XIX, 375, 1894. 



16 Pythium debaryanum, etc. Halle, 1874. 



