i6 



detect any cluster of terminal cells, as in the preceding species ; and 

 as some apices of the sterile leaves certainly terminate in a mucronate 

 point, we take this to be a distinctive difference between these allied 

 species; fresh plants must be examined to determine this matter with 

 certainty. Upper verticils are fertile and condensed in terminal and 

 axillary " heads, "some of which are very minute, others forming dense 

 clusters, 6 to 8 mm. in diameter. Leaves of the fertile verticils, 6, 

 very short, once or twice divided (occasionally a third division will be 

 noticed), first division 95 in diameter, terminals usually 4, or when 

 the ultimate node bears fruit 3, consisting of two cells, the lower 460 

 long, 80 in diam., not inflated, the terminal cell, mucro, 45 broad at 

 base, 140 long, tapering to a sharp point. Oogonia, usually on the 

 ultimate nodes, solitary, coronula persistent. Oospore 250-260 long, 

 240-245 broad, with 5 prominent spirals ; surface minutely granulated, 

 according to Nordstedt " grumous like felt with knotty fibres" like 

 pralonga. Antheridia 1 70 in diameter. The only collection of this 

 species was made by the late Dr. Thos. Morong on the 'island of Nan- 

 tucket, in July, 1887. 



Explanation of Plate. Fig. I, plant, natural size; Fig. 2, portion of a fertile 

 verticil X 2 5 5 Fig- 3> U P f a ^ ea ^ X 5 > Fig. 4, oospore ] ( 50 ; Fig. 5, sections 

 of membrane of spore, schematic, highly magnified. The Figs. 6-9 belong to N. 

 axillaris. 



NlTELLA ANNULARIS, Sp. 11OV. 



Plants 6 to 8 inches long, branched and forming intricate masses ; 

 lower verticils consist usually of six sterile leaves which in the middle 

 of the stem are often quite elongated, even exceeding the length of the 

 stem ; these are divided once oT twice into two or three elongated seg- 

 ments, the tips of the sterile leaves are surmounted by a crown of three 

 leaflets which are elongated and two-celled; the lower cell about 610 

 long, 290 broad the terminal (mncro) 200 long, 116 broad at base, 

 tapering gradually to a sharp point. The fertile verticils are very much 

 contracted and appear to terminate branches or peduncles from within 

 the sterile verticils in the middle portion of the stem, or terminate the 

 stems at the upper part, so that these " heads " are terminal. The fer- 

 tile verticils are usually somewhat branched and consists of an axis 

 with numerous whorls of fertile leaves ; these fertile leaves, though short, 

 are longer than the internodes of the axis, so that the fertile verticil 

 appears quite dense ; additional branches often arise within a fertile 

 verticil, so that it becomes compound and often unilateral in appearance 

 (see upper part of Fig. i). The axis stem is here about 500 in diam. 

 The fertile leaves are usually six, once divided, terminating in two or 

 three ultimate, two-celled leaflets ; the first segment of the leaves is 600 



