120 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN 



Sporangia are the only form of reproductive organs described for 

 A. iinipes and these would appear to be more uniformly uniseriate 

 or secund than we have observed them to be in ^. affine. 



From Acrochaetium robustum, which also we know only from 

 Dr. Bdrgesen's description and figures, A. affine would appear to 

 differ in being a taller plant (1-3.5 mm, vs. i mm. or less), in having 

 usually a single basal cell instead of a basal disc and in the larger 

 sporangia (18-27 ;u X 10-18 ju vs. 12-16^1 X 11 m)- No cysto- 

 carps are known in A. robustum, but the sporangia are abundant. 



Intermingled with the undoubted Acrochaetium affine we have 

 seen a few plants with a filamentous or rhizomatous endophytic 

 base, the original spore not differentiated and the basal filaments 

 apparently creeping within the outer cell walls of its host and 

 sending up erect external filaments here and there. We are 

 inclined to believe that they represent a condition of the plant 

 described above as A. affine, but not being wholly convinced as 

 to their identity, we have endeavored not to include them in 

 writing our diagnosis of this species. If they really represent a 

 form of A. affine, they would indicate a greater range of vari- 

 ability in the basal parts of an Acrochaetium than recent writers 

 on this genus have assumed to be possible. If our material 

 includes two species, it is possible that our figures 5 and 14, which 

 seem to show scarcely enlarged original basal cells, are to be re- 

 ferred to the species that we are leaving undetermined. Our 

 figure 14, by the way, is rather suggestive of B^rgesen's figure 

 (loc. cit. 51, /. 53) of the basal part of his Acrochaetium Hypneae. 

 In the matter of endophytic basal filaments, care must be taken, 

 in the case of A. affine, not to confuse the base of this plant with 

 the filaments of the endophytic Erythrocladia vagabunda and 

 E. recondita, with both of which it is often very closely associated. 

 Young few-celled filaments of E. recondita, in particular, often 

 closely encircle the partly endophytic bases of the Acrochaetium 

 and might easily be taken to be a part of it. On staining with 

 iodine, however, the protoplasts of the Acrochaetium become a 

 reddish brown, while those of the Erythrocladia become violet- 

 purple or almost black. 



