68 ISOETACEAE 



sparingly covered with rather low irregular often 

 elongate sometimes confluent crests serrate or 

 spinulose at apex and resembling cockscombs. 7. /. canadensis. 



Peripheral bast-bundles absent. 



Macrospores covered with tall simple or forked 

 spinules often recurved at apex and sometimes 

 slightly confluent. 3. /. ambigua. 



Macrospores sprinkled with distinct low granules 



resembling grains of sugar. 4. /. saccharata. 



Macrospores covered with tall jagged, straight or 

 curved, isolated or somewhat confluent crests; 

 spots of sporangium often composed of cells 

 fitted together in broad bands. 5. /. riparia. 



Sporangium not spotted. 



Macrospores 600-800 ji in diameter, covered with thickened 

 continuous crests occasionally anastomosing and forming 

 an irregular meandriform network. 1. /. macrospora. 



Macrospores 300-570 n in diameter, delicately honeycomb- 

 reticulated; stomata and peripheral bast-bundles present. 9. /. Engelmanni. 



1. I. macrospora Durieu. Distribution not known. 



Type locality " lake in the Catskills "; not since recorded with 

 certainty in our area. 



2. I. Tuckermani A. Br. In ponds: Newf. to Mass., Conn, and 



N. Y. 



Conn. Ledyard; reported also from North Stonington, East Lyme 



and Lyme. 

 N. Y. Lake Ronkonkoma, L. I.; also Peekskill, Westchester Co. 



3. I. ambigua A. Br.; Engelm. (I. Brannii Durieu). Lab. and 



Greenland to Alaska, south to N. J., Pa. and Cal. 



Conn. Scattered, but rare. 



N. Y. Rare on L. I., known otherwise only from Westchester and 



Ulster counties. 

 N. J. Bergen Co. and at Budd's Lake, Morris Co., also at Tom's 



River, Ocean Co. 

 Pa. Pocono, Monroe Co.; reported also in Wayne, Lackawanna 



and Carbon counties. 



4. I. saccharata Engelm. Eastern Maryland, and District of 



Columbia. Also in New Jersey? Limits of distribution not 

 known. Said to intergrade with I. canadensis. 



N. J. Reported from Camden Co., and Mantoloking, Ocean Co. 



