LAQENIDIACEAE 



81 



at the ends, rarely branched, continuous and unicel- 

 lular with the short infection tube and zoospore case 

 persistent. Sporangia and zoospores unknown. 

 Oogonia globular, oval and almost spherical; be- 

 ginning as a terminal <>r intercalary swelling and 

 wit li further growth becoming somewhat lateral in 

 position luit continuous with the main axis. Antheri- 

 dia oval, clavate, and cone-shaped; borne on the 

 oogonium and delimited from the latter by a cross 

 wall ; usually disintegrating and disappearing after 

 fertilization; conjugation tube usually well-devel- 

 oped and conspicuous. Oospores single, rarely 



double, spherical, oval, ellipsoid and egg-shaped, 

 I i 19/1 in diameter, with a thick rough or warty 

 wall: content granular with one or more refractive 

 globules; germination unknown. 



Parasitic in the oogonia of Chara in Switzerland. 



De Wildeman created the genus Lagenidiopsis as 



an intermediate group between the I.agcnidiales and 



l'cronosporales. primarily because the thallus is 

 filamentous and unicellular. These characters, how- 

 ever, are no longer of significance in this case, since 

 similar thalli have subsequently been found to be 

 characteristic of certain species of Lagenidium also. 

 Furthermore, the method of sexual reproduction in 

 LagenidiopsU is typical of that in the former genus, 

 and on these grounds it seems logical to merge the 

 two genera. Their identity or difference, however, 

 cannot be definitely settled until the sporangia and 

 zoospores of LagenidiopsU have been found. 



L. MARCHALIANUM «V Wildeman, 1897. Ann. Soc. 

 Beige Micro. SI: 8. PI. 1, figs. 1-9. 



Thallus filamentous, cylindrical. 2.2-6.7 /* in di- 

 ameter, sometimes irregularly swollen, slightly or 

 not at all constricted: occasionally confined to a 

 single cell, but usually extending through six or seven 

 host cells; enlarged up to 7 \i. in diameter before 

 entering the cross septa of the host and constricted 

 to 1 ;i as it passes through. Sporangia cylindrical, 

 elongate. 30-60 p, narrowly spindle-shaped with a 

 delicate. 1.5-2 ft thick, exit tube which extends \ 5 \>. 

 beyond the host cell. Zoospores unknown. Oogonia 

 spherical. 20ft, intercalary, rarely terminal; an- 

 theridia adjacent to oogonia on the same filaments, 

 or arising as a branch from an adjacent filament. 

 Oospores spherical, 8-14 /x. hyaline, smooth, thick- 

 walled, rarely parthenogenetic; germination un- 

 known. 



Parasitic in Oedogonium sp. in Belgium (de 

 Wildeman, I.e. ) and Virginia. L*. S. A. (Couch. '35 | . 



L. OEDOGON1I Scherffel, 1903. Hedwigia 41: (105). 

 1925. Arch. Protistk. 52: 109. PI. :,, figs. 209-219. 



Thallus usually single, rarely two or more in a 

 cell, ovoid, vesicular, 20-25 /' .■' 35—52 //. irregular. 

 lobed. with blunt protuberances, rarely filamentous. 

 filaments when present several hundred microns in 

 length and coiled; non-septate and continuous with 

 One exit tube which may end .almost Hush with the 

 surface of the host cell or extend considerably be- 

 yond it. Zoospores mono- or diplanetic ; fully formed 



in the sporangium or delimited in an extramatrical 

 vesicle with an indistinct membrane; in the former 

 Case emerging singly and encysting in a group at the 

 mouth of the exit tube, later germinating and leal 

 ing the t li.fi /■ in diameter, cysts behind as in .leh- 

 lya; secondary zoospores or swanners pointed at 

 the anterior and round at the posterior end with a 

 ventral groove, heterocont with the short llagellum 

 directed forward; forming an apprcssorium on the 

 host wall in germination. Oospores globular, spheri- 

 cal. 12-1 t/i, with a 2 p. thick, hyaline, smooth wall 

 and containing coarsely granular protoplasm and a 

 large eccentric globule; germination unknown. 



Parasitic in Oedogonium sp. in Hungary (Schcr- 

 fifel, I.e.) and Missouri, U. S. A. (Couch, '35). 



This is a significant species because its zoospores 

 exhibit several characteristics common to Pythium 

 and Achlya. The zoospores may be formed extrama- 

 trically in a vesicle as in Pythium, or within the 

 sporangium and then emerge and encyst at the 

 mouth of the exit tube as in Achlya. It is to be noted 

 in this connection that the zoospores of Olpidiopsis 

 Oedogoniorum have the same characteristics, while 

 its resting spores and their method of formation are 

 also strikingly similar to the oospores of L. Oedo- 

 gonii. Scherffel accordingly pointed out that O. 

 Oedogoniorum has much in common with Lageni- 

 dium, and was of the opinion that it may relate to 

 the latter genus. From his drawings and descriptions 

 of the thalli one might believe that the two species 

 are closely related or even identical, but the elongate 

 thalli of L. Oedogonii which Couch figured are dis- 

 tinctly unlike those of Olpidiopsis. It is nevertheless 

 obvious that further study and comparison is very 

 essential to an understanding of the two species. 



In this species Scherffel found segments of the 

 thallus or possibly of sporangia the contents of 

 which had contracted, become septate, and thick- 

 walled. He regarded these resting structures as com- 

 parable with the gemmae of the Saprolegniaceae, 

 but it is doubtful that they are of any particular 

 morphological or phvlogenetic significance. 



L. SACCULOIDES Serbinow, 1924. I.a Defense ties 

 Plantes 1 : Hj. 



Thallus short, unicellular, sac-like with lobes or 

 short branches, or narrowly elongate, .'5.5-7.6 jj. in 

 diameter, with occasional septa. Zoospores appar- 

 ently completing their development in an extrama- 

 trical vesicle; spherical, 3.5 ft, in fixed and stained 

 preparations; position and relative lengths of fla- 

 gella and presence of diplanetisin unknown. Sexual 

 reproduction isogamous ; contents of two adjacent 

 cells flowing together and forming a zygospore (?) 

 in the space between them. Zygospores hyaline, 

 spherical, 13.8 p., oval, elongate. 7.6 ft X 15.2 /x, 

 with a sculptured outer .and a smooth inner wall; 

 containing a large refractive globule; germination 

 unknown. 



Parasitic and saprophytic in Closterium ralflii 

 var. hybridum in the Menzelinsk district of the 

 Ufimsk province in Russia. 



