716 MINNESOTA BOTANICAL STUDIES. 



Arthrocardia f frondesccns (Post, et Rupr.) Aresch. in J. Ag. 

 Spec. Alg., II., p. 549. 



f. maxima, f. nov. PI. LIL, Fig. 3. 



Fronde majore et crassiore ; articulis pinnarum lobis latissimis 

 saepe crenulatis, apicalium compressis obovatis vel spatulatis. 



f. intermedia, f. nov. PI. LIL, Fig. 2. 



Fronde tenuiore ; articulis pinnarum compressis deltoideo- 

 obcordatis lobis nonnunquam acutis. 



f. polymorpha, f . nov. PI. LIL, Fig. 4; PI. LVL, Figs. 6, 

 6a and 7. 



Fronde minore ; crassiuscula, polymorpha : turn articulis pin- 

 narum obcordatis, obreniformibus vel sagittatis, apicalium obo- 

 vatis vel globosis ; turn articulis pinnarum axiumque cylindra- 

 ceis, linearibus vel globosis. 



Ruprecht's illustrations and description /. c. precisely coincide 

 with f. typica. Areschoug remarked in J. Ag. Spec. Alg. /. c. 

 that the original plant might have been a tiny form of the spe- 

 cies. We have at Port Renfrew plants often attaining to several 

 centimeters in height. 



f . typica is a densely caespitose plant, irregularly pinnated ; 

 the lowermost pinnae attain to the length of the main stem, and 

 thus give the appearance of trichotomy. The articuli are com- 

 pactly arranged, the lower margin of an articulus in contact 

 with the upper margin of the subsequent one. Conceptacles 

 are mostly found two to four in number and placed on the 

 shaded surface, often, however, solitarily immersed at the 

 angles of a deltoid articulus. 



f. maxima is distinguished from the other formae by its large 

 and compressed articuli at the upper portion of the branches. 

 These articuli measure 2-5 mm. broad, 1.5-2 mm. long and 

 are often cleft at their lobes. The branches are not so dense as 

 in f . typica. 



f. intermedia is characterized by having the upper portions of 

 the fronds revoluted downwards while it is yet young. The 

 articuli are rather less wide than those of f. typica and in every 

 part thin. The lobes of the articuli are angled and consequently 

 more loosely arranged. 



f . polymorpha attains to a length of scarcely one inch and 

 has its articuli thick and rough. Its form is very variable, some- 

 times assuming quite an aberrant appearance (PL LVL, Fig. 6, 



