26 



THE SIMPLE HOLOCARPIC BIFLAGELLATE PHYCOMYCETES 



Eurychasma in method of infection and develop- 

 ment, but, according to Sparrow, it differs funda- 

 mentally by the presence of comparatively narrow 

 exit tubes, its completely intramatrical position in 

 the host, the encystment of the zoospores outside the 

 sporangium, and by a more pronounced effect on the 

 host cell. However, differences in number, length 

 and diameter of the exit tubes, effect on the host, 

 partial or complete intramatrical development are 

 questionable generic characters, and when Eury- 

 chasmidium as well as Eurychasma are more fully 

 known they may possibly prove to be identical. 



Sparrow reported that zoospore germination and 

 infection of the host are similar to those of Eury- 

 chasma and Ectrogella, although he did not actually 

 observe these processes. In a few cases, however, he 

 found empty zoospore cases and infection tubes at- 

 tached to p'arasitized cells (fig. 6), which suggests 

 that the contents of the spore enter the host cell as a 

 naked body. Multiple infection apparently occurs 

 fairly often, since as many as eight thalli may be 

 found in a single cell (fig. 3). The well-established 

 thalli are easily distinguishable in the host cell by 

 the presence of numerous refractive globules in the 

 protoplasm (figs. 5-9). As growth continues the 

 chloroplasts begin to disintegrate and the remainder 

 of the host protoplasm becomes quite vacuolate (figs. 

 6-7). Concomitant with these internal changes the 

 host cell becomes distended and its wall greatly 

 thickened (figs. 8-10). Infected cells do not divide, 

 but healthy cells of adjacent nodes are stimulated to 

 divide. There are thus formed in the vicinity of 

 parasitized cells a number of curved stunted lateral 

 branches (fig. 8, 9) which give a bushy appearance 

 to the infected regions of the host plant. 

 < The successive internal maturation changes in the 

 parasite are identical to those described by Peter- 

 sen for Eurychasma, including the characteristic 

 "stade ecumeux." The final stages in zoospore for- 

 mation and emergence have not been observed, so 

 that it is not known whether the zoospores become 

 flagellate and swarm within the sporangium or glide 

 out without flagella. In either event, they come to rest 

 and encyst in loose masses at the mouth of the exit 

 tubes (fig. 10). The cystospores thus formed (fig. 

 11) are polygonal in shape, and after a period of 

 quiescence the protoplasm of each cyst emerges 

 and develops into a flagellate zoospore. Sparrow 

 reported that the zoospores are biflagellate, but he 

 did not illustrate them and say whether they are 

 iso- or heterocont, nor show at what place the fla- 

 gella are attached. As far as the writer is aware 

 the zoospores of this genus have never been illus- 

 trated. 



E. TUMIFACIENS (Magnus) Sparrow, I.e., figs. 14-21. 



PI. 1, fig. 1. 

 Chytridwm (Olpidium) Pumifaciens Magnus, 1872a. 

 Sitz'b. Gesell. Nat. Freunde Berlin, 1872:87. 1872b. 



Jahresb. Komm. Untersuch. Deut. Meere Kiel 2:61. 

 PI. 1, figs. 1-16. 1873. Hedwigia, 12: 28. 

 Olpidium tumifaciens (Magnus) Fischer, 1892. Raben- 



horst's Krypt. PI. 1, IV: 27. 

 Pleotrachelus tumifaciens (Magnus) Petersen, 1905. I.e., 



p. 456. 

 Zoosporangia, hyaline and smooth, spherical, 

 100-1 10 ^, ellipsoid, 110 X 200 n, irregular and 

 lobed with 1 to 30 exit tubes. Zoospores hyaline with 

 a single refractive globule, eliptical, 3 X 5 1^- Addi- 

 tional details are given in the generic diagnosis 

 above. 



Parasitic in Ceramium fiabellic/erum and E. acan- 

 thonotum in Scotland (Magnus, I.e.) and England 

 (Smith and Ramsbottom) ; a red alga in Belgium (de 

 YVildeman '00) ; Ceramium sp. and C. diaphanum in 

 the United States ( Murray, '03 ; Sparrow, I.e.) ; and 

 Ceramium rubrum in Denmark (Petersen, I.e.). 



According to Magnus, this species was first ob- 

 served by Cramer in 1855 (pi. 11, figs. 9, 11) at 

 Naples, Italy, who mistook it for a monstrosity of 

 C. flabelligerum (C. spiniferum). Sparrow believed 

 that the organism which he observed at Wood's Hole 

 is the same as Magnus' species, but there are some 

 differences in the accounts of it given by the two 

 authors. Magnus described the zoosporangia as soli- 

 tary or numerous in a cell with one or two exit tubes 

 which extend considerably beyond the algal cell, but 

 he failed to observe any marked thickening of the 

 host wall. Sparrow, on the other hand, reports that 

 the wall is abnormally thickened, while the zoo- 

 sporangia may possess as many as thirty exit tubes, 

 through which the ellipsoid, biflagellate zoospores 

 emerge. These differences may well be due to the 

 limited observations of Magnus, but there is none- 

 theless a possibility that Sparrow may have studied 

 a different species. 



plate 7 

 Eurychasmidium tumifaciens 



(Figs. 1-4 after Magnus, '72; figs. 6-11 after Sparrow, 

 '36.) 



Fig. 1. Young thalli in the apical hair cell of 0. flabel- 

 ligerum. 



Fig. 2. Older tliallus in same type of cell. 



Fig. 3. Enlarged cell with eight spherical thalli. 



Fig. 4. An enlarged apical cell containing a mature 

 tliallus with two broad exit tubes. 



Fig. 5. Early developmental stage of tliallus in Cera- 

 mium diaphanum. 



Fig. 6. More mature tliallus with zoospore case and in- 

 fection tube still attached to the enlarging host cell. 



Fig. 7. Tliallus surrounded by vacuolate host proto- 

 plasm. 



Fig. 8. Tliallus completely filling host cell, the wall of 

 which is greatly thickened. 



Fig. 9. Lobed irregular, vacuolate tliallus. 



Fig. 10. Empty sporangium with numerous short exit 

 tubes; groups of cystospores near the exit tubes. 



Fig. 11. A group of polygonal cysts. 



