152 THE LOWER FUNGI— PHYCOMYCETES 



family. These bodies are usually developed at the ends of the 

 hyphae in chains. They are unicellular, globose to ovoid or 

 pyriform, thick-walled resting spores, and fall apart easily at 

 the dividing septa. After a resting period of variable length 

 they germinate by a germ tube on which a sporangium is usually 

 soon formed. The chlamydospore never germinates directly 

 by swarmspores, and in this respect differs distinctly from the 

 resting sporangium. Chlamydospores are often developed 

 abundantly, and species occur (Humphrey, 1893: 83; Weston, 

 1917) in which the sexual spores seem to have been completely 

 replaced by them. Some authors avoid the term chlamydospore, 

 preferring gemma, conidium, or resting spore. 



The sexual organs are developed on the external mycelium, 

 and are usually terminal in position, though occasionally inter- 

 calary. The oogonium, arises as a swelling of the hypha which 

 bears it (oogonial branch), and at maturity is definite in form. 

 If terminal it is usually more or less globose, if intercalary 

 barrel-shaped. Its wall becomes thickened by the deposit of 

 new material on the inner surface, this new layer failing to give 

 the reaction for true cellulose characteristic of the primary wall. 

 Scattered over the wall in some species a varying number of 

 small circular thin spots or pits occur. These constitute points 

 at which the secondary thickening has failed to take place. It 

 was formerly supposed that the fertilization tubes from the 

 antheridia enter at these spots, but this has been shown not 

 to be necessarily true. Though the function of the pits is 

 unknown they are striking in appearance and of taxonomic 

 importance in certain forms. 



The antheridial branches are slender and lateral. The 

 antheridium is cut off at the tip of the antheridial branch. It 

 is cylindrical or clavate in form, and somewhat thicker than the 

 branch. It is usually applied to the oogonium in such a fashion 

 that its side rather than its tip is in contact with the oogonial 

 wall. In some species antheridia are absent or only rarely 

 formed. Not infrequently several are found attached to a single 

 oogonium. 



The same primary hypha may bear both oogonial and antherid- 

 ial branches or only those of one sex. In ordinary cultures it is 

 often impossible to determine whether two hyphae belong to 

 the same or different thalli, and since single spores have been 

 used as the starting point for cultures in only a few cases, it 



