222 Puget Sound Marine Sta. Pub. Vol. 1, No. 20 



unsuccessful, because they are taken readily by the heavy membranous wall 

 surrounding the fungus, and are not readily drawn from it. The spores 

 themselves stain slowly and destain quickly. The granular appearance of 

 the spores within the sporangia (Fig. 6) was best observed in freehand 

 sections quickly dehydrated, stained with erythrosin, and mounted in bal- 

 sam. During the process of dehydration and infiltration to make paraffin 

 blocks, many of the sporangia were broken off, since they protruded 

 through the pellicle. In freehand sections more of them remained intact. 



The life history could be clearly traced with the exception of that 

 portion spent outside its host, probably as a free-swimming zoospore. In 

 the earliest stages of its development found (Fig. 1 ) it was a small spher- 

 ical body, with a heavy membrane surrounding it. A little later (Fig. 2) 

 it showed considerable elongation, with the long axis perpendicular to the 

 surface of the host. The host cell containing the' fungus elongates at the 

 same time, sometimes reaching many times its original length. The cell 

 may be wholly filled by the fungus but more frequently it is not. The 

 parasitic body thru growth becomes oval, then oblong, then cylindric. 

 Later the outer end is drawn out to resemble a neck or finger-like projec- 

 tion of the more deeply imbedded body of the parasite. The contents of 

 the membranous bag is forced -outward, thru the narrow finger, enlarging 

 the tip under the pellicle (Figs. 3-4). The outer swelling becomes the 

 sporangium. It elongates rapidly and the walls of the imbedded portion 

 contract, forcing the contents outward into the sporangium. During its 

 development the sporangium forces its way to the surface, becoming 

 epiphytic (Figs. 5, 6). If the sporangium is not too long it may stand 

 erect, but more commonly it turns to one side like the bowl of a pipe (Fig. 

 5). That portion of the membranous covering within the host then shriv- 

 els up slowly, or becomes perforated with holes, and seems to be disin- 

 tegrating. In the older portions of the midribs examined the sporangia 

 were empty and deteriorating rapidly. 



In the early stages of development of the fungus no rhizoids are 

 found (Figs. 1-4), but as the fungus approaches maturity blunt rhizoids 

 are sent out between host cells, or even project into the sides of adjacent 

 cells, pressing in their sides, but not penetrating the walls (Figs. 5-10). 

 In some cases rhizoid-like structures are sparingly developed, while in 

 others they are sufficiently numerous to make the surface of the endophytic 

 portion of the fungus quite rough. 



In a previous paper the writer (6) described papillate bodies on the 

 surface of the sporophylls of Alaria fistulosa. An hypothesis there ad- 

 vanced as to one cause of these elevations was that the outer portions of 

 the sporangia of the alga crowded one another and compelled the tissues 

 to rise, thus giving greater surface for the fruiting layer. Another cause 



