MONOBLEPH ARID ALES 739 



superimposed series of oogonia at its tip. Length of hypha 1-2 mm., 

 diameter varying from 5 to 14 [x (majority 7-9 \x); attached to the sub- 

 stratum by branching rhizoids. 



"Oogonia arranged singly, or in rows of 2-16 (average 9), formed in 

 basipetal succession, at the tips of the hyphae. The long chains of super- 

 imposed oogonia are very characteristic of this variety. Occasionally 

 intercalary oogonia are formed. Oogonia are usually cylindrical in 

 shape, but occasionally irregular, opening when the oosphere is formed 

 by a tube or 'neck' which may be curved or straight. The neck is very 

 variable, long- and short-necked forms being found in the same series 

 of oogonia. The oogonia vary in length from 25 to 54 ;x (majority 36-43 

 \x), diameter 14-36 ;x (majority 21-25 [x). 



"Antheridia normally, but not always, present, varying from sub- 

 conical to cylindrical in shape, tapering at the tip, narrow, usually 

 straight, but occasionally slightly curved; length 7-29 \x (majority 14 21 

 fx); diameter 5-14 \x (majority 7-9 ;x). The majority of antheridia are 

 longer than the neck of the oogonium, although some may be equal in 

 length or shorter than it; as a rule borne upon the terminal wall of the 

 oogonium (epigynous), to one side of the neck, but occasionally hy- 

 pogynous and intercalary in position, opening by an exserted tube formed 

 just beneath the oogonial cross-wall. A single antheridium usually con- 

 tains 5-7 amoeboid and uniflagellate antherozooids which measure 

 3.5-7 [x by 3.5 jx. Protandry is well marked. 



"Each oogonium contains a single oospore which matures and ger- 

 minates in situ (endogenous). Oospores golden brown, smooth, and very 

 variable in shape, spherical, cylindrical, irregular, and widely ellipsoid 

 forms being found (ellipsoid form the most typical); length 18-32 ;x 

 (majority 23-25 [x); diameter 11-25 \x (majority 20-21 jx). Much var- 

 iation in oospore size is found, even among oospores contained in 

 oogonia borne on the same filament" (Perrott, he. cit.). 



On submerged twigs of Quercus robur, Fraxinus excelsior, Great 

 Britain. 



Resembling var. insignis in every way except for smaller size and 

 frequently parthenogenetic oospores. Var. minor was also found living 

 on the same twig as the typical var. insignis. 



