62 



COMPARATIVE MORPHOLOGY OF FUNGI 



do not find an exit and remain in the zoosporangium may germinate 

 there and pierce the walls. 



At the appearance of unfavorable conditions, antheridia and oogonia 

 are formed in some segments instead of sporangia (Fig. 36, 2 to 4). 

 The antheridium remains cylindrical and contains few, often only two, 

 nuclei. The oogonia swell and become barrel shaped; usually there are 

 about eight nuclei. At maturity all female nuclei except one degenerate; 

 it is still uncertain whether this lies in a special oosphere. A neighbor- 

 ing antheridium, generally of the same, rarely of another plant, forces a 

 copulation tube through the wall of the oogonium, into which a single 

 nucleus migrates and soon fuses with the female nucleus. An oospore 



Fig. 37. — Ancylistes Closterii. 1. Closterium with parasite. 2, 3. Fertilization. 



Mature zoospores. (After Dangeard, 1906.) 



with a double wall develops and probably germinates by zoospores which 

 escape through the neck. 



Lagenidium Rabenhorslii (Zopf, 1885), causing an epidemic on the 

 mats of Spirogyra, Mesocarpus, etc., and L. pygmaeum (Zopf, 1888) on 

 Pinus pollen in water, agree essentially with Myzocytium, except that 

 their mycelium is lobulate. The sporangia discharge undifferentiated 

 protoplasm into a germ sac formed at the mouth of the emission collar. 

 The sac begins to rotate, bursts and liberates the biflagellate zoospores. 

 Occasionally in L. americanum there is no differentiation into zoospores, 

 but the naked protoplasm swims away with many flagella (Atkinson, 

 1909). 



In Ancylistes Closterii on Closterium, the emission collar develops 

 to a regular hypha into which the sporangia discharge their whole 

 content. From time to time they are abjointed in the rear from the 



