432 Schneider: Chroolepus aureus a lichen 



substratum and require the same or similar moisture and light 



conditions. 



The interesting feature, however, was a delicately reticulate, 

 spirally wound, network of what appeared to be the hyphal tissue 

 of a fungus which entirely enwrapped the algal threads from base 

 to apex and projected a short distance beyond the apex of most 

 threads. In some instances, this structure extended only to the 

 apex or wq'thin a short distance of the tip. This network is very 

 firmly attached to the algal cell-wall. Only after the application 

 of strongly alkaline or strongly acid solutions was it possible to 

 induce it to separate from the algal cells, assisted by pressing the 

 material quite forcibly under the cover-glass. Even then, only 

 fragments could be removed which showed the reticulation very 

 clearly (see plate). The network gives to the filaments a rough- 

 ened appearance, with here and there a delicate thread (simple or 

 sparingly branched) of the network projecting out from the algal 

 filament. As stated, this mesh-work extends a short distance be- 

 yond the apex of the algal thread, in the form of a tube, partially 

 divided across by the same network, thus giving the semblance of 

 partial septation. One, two, or three of these compartments were 

 noticeable, never more. It appears that the compartments are 

 occupied by the new algal cells as the filament grows in length ; 

 however, new mesh compartments are always formed in advance 

 of tlie algal cells. 



It would appear that this finely reticulate, colorless network is 

 the hyphal tissue of a fungus which invests the algal filaments, 

 indicating a very intimate biological relationship. It represents a 

 condition not unlike that which exists in the well-known lichen 

 EpJiche pubesccns Fr., only the fungal symbiont does not penetrate 

 the algal tissue. The hyphal structure of the fungal symbiont in 

 both is closely similar excepting that the anastomoses are much 

 more common in Chroolepus aureus. No experiments have been 

 made to determine the biological relationship of the two symbi- 

 onts, whether antagonistic or mutualistic. Nor was It possible, 

 at the time, to determine conclusively whether or not the fungal 

 symbiont is always present. It was present in all of the material 

 examined, although specimens were found in which the reticula- 

 tion was rather indistinct. Some authors .speak of this terminal 



