CLASS ARCHIMYCETES 



19 



apparently the plasma membrane may be ruptured at any point. A 

 sexual differentiation is also lacking, indeed two gametes, after attempt- 

 ing to copulate for a few minutes, may again separate. This inner 

 differentiation rests rather on differences in age or turgor. 



The young diploid protoplast is binucleate (Fig. 9, 10). When it is 

 mature it is surrounded by a membrane which in time differentiates 

 into an exospore and endospore. Thereby the zygote has become a 

 hypnospore. A fusion of both nuclei occurs in the following spring a 

 few days before germination (Fig. 9, 11). This is followed by numerous 

 mitotic divisions, of which the first is possibly a meiosis. The outer 

 layer of the endospore swells, whereupon the inner layer of the endospore 

 forms an emission collar through the wall of the host cell (Fig. 9, 12) 

 and discharges the zoospore. 



Thus the life cycle corresponds to the following scheme (Goeldi and 

 Fischer, 1916): 



R 



Zoospores P 



Binucleate 



ZoUpore S ^™ u £^oosporangia^Gam 



Diagram III. 



Haplont and diplont are motile in their young stages and independent 

 in their life functions; accordingly they are true gametophytes and sporo- 

 phytes. The former, which lacks the diplont may increase repeatedly 

 by zoospores, while the specific duty of the latter 

 is the formation of hypnospores. 



A similar life cycle is probably possessed by 

 the numerous other equally parasitic species of 

 Olpidium, as 0. Brassicae, a destructive parasite 

 of seedlings of cabbage, possibly also of lettuce 

 and tobacco. The young protoplasts are uni- 

 nucleate. Under favorable conditions they 

 may be naked, even in the stage with 32 nuclei. 

 Then they are surrounded by a membrane and 

 on the proximal side develop an emission collar 

 which germinates at the tip (Nemec, 1912). 

 The source and germination of hypnospores rangia. 2. Hypnospores within 



/-r-.- ,~ «n ■ , t n i epidermal cells. (X 110; after 



(Fig. 10, 2) is unknown. In youth, however, Woronint i 878 .) 



they are binucleate, suggesting a previous plas- 



mogamy (Nemec, 1922). Similar observations have been made on 0. 



Salicorniae on the roots of Salicornia herbacea (Nemec, 1911). 



Similar to Olpidium, but lacking an emission collar, is Olpidiaster 

 radicis (Asterocystis radicis) parasitic on the secondary roots of many 



Fig. 10. — Olpidium Bras- 

 sicae. 1. Germinating zoospo- 



