INTRODUCTION 25 



Species of Gonapodya may be found on submerged twigs and fruits. 

 Monoblepharis occurs for the most part on old undecorticated sunken 

 twigs, particularly of birch and ash, in clear, often cool, water. If a 

 few such twigs are placed in battery jars of pure water and kept at 

 about 1 1° C, the growth of Monoblepharis is particularly favored. The 

 fungus may form dense pustules or a complex of delicate hyphae 

 covering the whole twig. Monoblepharella has, thus far, been recovered 

 primarily from tropical soils, where it often occurs with Allomyces 

 (see above). It grows readily on hempseed bait. 



Those members of the Plasmodiophorales which are parasitic on 

 aquatic Phycomycetes are sometimes found in old gross water cultures. 

 The fungi parasitic on aquatic phanerogams produce (with the exception 

 of Lignierd) conspicuous hypertrophy of the host, a fact which aids 

 in the recognition and collection of infected material. 



The simpler members of the Saprolegniales (Ectrogellaceae, Thraus- 

 tochytriaceae) occur on fresh-water and marine algae. Species of Ectro- 

 gella often develop in Petri dishes of fresh-water diatomaceous scum 

 left in a cool light place in the laboratory for a few days. One marine 

 form, E. perforans, is very common on marine species of Licmophora, 

 a stalked diatom epiphytic on littoral seaweeds. Parasitic marine forms 

 such as Eurychasma and Earychasmidium are local; the former, for 

 example, has been found by the writer to occur in the Kattegat only 

 on the phaeophycean Striaria growing on a clay bottom. The rhodophy- 

 cean Ceramium infected by Eurychasmidium may frequently be detected 

 by the presence on it of numerous short, abnormal, lateral branches. 

 Thraustochytrium proliferum has been collected on disintegrating plants 

 of the green alga Bryopsis and on the rhodophycean Ceramium diaph- 

 anum. It is usually found on material in shallow dishes into which 

 fresh sea water is allowed to drip constantly. Saprophytic species of 

 the Saprolegniaceae occur on bits of substrata of both plant and animal 

 origin. The cadavers of insects or their larvae, dead fish, twigs, flowers, 

 fruits, and so on, are all favorable sources of food. Split boiled seed of 

 hemp {Cannabis sativa) is now extensively used as bait as well as for 

 the maintenance of these fungi in gross water cultures. It has proved 

 an exceedingly favorable medium, with the distinct advantage of being 

 less likely to become fouled by bacteria and protozoa than are flies, 



