Il6 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN 



factorily as in the case of E. recondita, but from the general simi- 

 larity of the supposed carpogonia and sporocarps to those of 

 E. recondita we feel no doubt as to its existence. In two instances, 

 we have seen a supposed spermatium resting on the general 

 surface above a supposed carpogonium. We have not observed 

 any carpogonium beak or trichogyne and think it must be only 

 slightly developed, if present at all. 



The partly endophytic base of Acrochaetium affine, which some- 

 times develops short endophytic filaments or rhizoids, is occa- 

 sionally found in such close contact with Erythrocladia vagabunda 

 that it requires careful observation to satisfy one's self that the 

 two things are not in organic continuity. The iodine stain, how- 

 ever, is an effective help in differentiating the two, the protoplasts 

 of the Acrochaetium reacting with a reddish brown rather than a 

 violet coloration. 



Acrochaetium infestans sp. nov. 



Endo- and epizoic, minute; interior filaments tortuous, intri- 

 cate, serpentine, or labyrinthine, mostly 2.0-5.5 ^ in diameter, 

 thin-walled, the branching very irregular, lateral, subdichotomous, 

 or very rarely opposite, commonly divaricate from near the middle 

 of a cell, the branches often subcircinately reflexed or infiexed, the 

 interior cells mostly 12-60^1 long, 3-18 times as long as broad, 

 commonly curved or contorted and of irregular or fluctuating 

 diameter, the terminal cells of branches often enlarged, subhaniate, 

 irregularly clavate, or subdivaricately forking, sometimes attaining 

 a diameter of 7-8 m, or, rarely, interior filaments forming a sort 

 of pseudoparenchyma, with irregular cells sometimes 10-13 /x 

 broad; chromatophore small, substellate or irregularly discoid, 

 near the center of the cell or subparietal, showing a single pyrenoid ; 

 sporangiiferous filaments external, up to 90 m high (or 230 ix, 

 including hairs), the simpler consisting of a single pedicel cell 

 bearing 1-3 sporangia (or, very rarely, the exsertcd sporangium 

 sessile on an endozoic filament), the larger showing 1-9 short, 

 1-3-celled, rarely secund branches, the cells 4.5-6.5 M in diameter, 

 1-2 times as long as broad; hairs commonly present on the larger 

 external filaments, flexuous and attaining a length of 125-170 /x; 

 sporangia terminal or lateral, solitary, binate, or tcrnate, ovoid 

 or ellipsoid, 10-14 M X 6.0-8.5 /i- [Plate 14.] 



In and on the stalks, stolons, and less commonly hydranths of 

 small campanularian hydroids (perhaps representing more than 

 one genus) attached to Dictyota dichotoma and other algae, dredged 



