698 AQUATIC PHYCOMYCETES 



the fungus will form a loose filmy mass, or, more often, it will occur in 

 definite pustules on the surface of the fruit in association with Blasto- 

 cladia and Rhipidium. The surest method of obtaining such fruit-inhabit- 

 ing fungi is to construct traps of galvanized wire screening, place the 

 fruits inside, and subn'ierge them in some likely aquatic habitat. Such 

 traps when left for at least a month will usually yield an abundance of 

 Gonapodya and other Phycomycetes. After examination the fruits may 

 be placed in jars with a relatively large amount of water, left at a low 

 temperature (3-8°C), and examined at intervals. Further details of 

 these culture methods may be found in papers by Kanouse (1926, 1927). 



Development and Morphology 

 the thallus 



Since more is known about the development and morphology of 

 Monoblepharis than about that of any other member of the order, em- 

 phasis is placed on it throughout this section. 



The zoospore of Monoblepharis upon germination may produce two 

 germ tubes, one giving rise to the holdfast system which anchors the 

 plant to the substratum, the other producing the main body of the plant. 

 According to Lagerheim (1900), holdfasts may also be formed by the 

 ramifying hyphae. 



Once the fungus is established there results, under favorable condi- 

 tions, an abundant mycelial growth, the nature and extent of which 

 appear to depend somewhat on the particular species. For example, 

 in Monoblepharis maerandra the growth and branching may be exceed- 

 ingly profuse and may result in a solid mat of interlocking tangled 

 hyphae covering the substratum, whereas in the other species the fila- 

 ments seem more rigid and less branched, and tend to remain separated 

 from one another. The finely granular content of the hyphae, in which 

 are occasional refractive granules, is usually disposed, because of the 

 regularly placed vacuoles, in a reticulate or foamy manner. The striking 

 effect produced by this type of vacuolization makes it comparatively 

 easy for one to recognize, even in the vegetative state, a member of the 

 Monoblepharidales. Under changing environmental conditions the pro- 

 toplasm may temporarily assume a nonvacuolate homogeneous texture. 



