42 THE NORTH AMERICAN SLIME-MOULDS 



color from nearly pure white, through different shades of gray 

 to brown fuliginous or black ; hypothallus none or obscure ; 

 columella none ; capillitium abundant, the white lime knots vary- 

 ing in size and shape, connected by rather long hyaline threads, 

 with here and there an empty node ; spore-mass black, by trans- 

 mitted light, dark, sooty brown, minutely papillose, 10-11.5 /* 



This remarkable species, while not at all difficult of recog- 

 nition to one familiar with its phases, is withal very difficult to 

 define. Normally stipitate, it often shows from the same plas- 

 modium all sorts of forms, the shape of the fructification de- 

 pendent apparently upon external conditions prevalent at the 

 time. The amount of lime also varies, especially in the capilli- 

 tium, where there is always a tendency to the formation of 

 something like a pseudo-columella. The outer capillitium is 

 sometimes nearly destitute of lime. The lime in the stipe also 

 varies ; the black or brown stipes are of course free from lime, 

 the white ones calcareous. Among the white-stemmed phases 

 occurs a form in which a globular sporangium is borne upon a 

 tall, slender stipe, twice the width of the sporangium or greater. 

 This type is Pliysannn affine Rost. According to Rostafinski 

 typical forms of P. ncfroidcwn have the stalk black, while 

 P. affine has the stem white or gray, but surely the species can- 

 not be distinguished on this basis, for the same plasmodium 

 yields stipes of all shades. 



The synonymy of the species is perplexing. The original 

 description of P. compression by Alb. and Schw. is far from 

 sufficient. Link called (Rostafinski teste) the same thing P. 

 griseum Link and P. comprcssum Alb. and Schw., besides 

 including forms which are in no way related. Trichia cernua 

 Schumacher, which Fries makes a Physarnm, is certainly 

 TilmadocJie nutans. Didymium connatum Peck is the form 

 before us, but the combination P. connatmn is already a 

 synonym. For these reasons Rostafinski's name is to be pre- 

 ferred. P. conncxum Link, as revised and presented by Morgan, 

 is certainly our present species. P. conflnens Pers., by the tes- 

 timony of the European writers, is a Didymium. It is difficult 



