Azolla Salviniaceae 59 



I did not take a specimen because I was not prepared to care for it. This 

 is the only specimen I have ever seen on a tree in Indiana although it is 

 common in this habitat in the South. 



Md., 111., and Mo., sotithw. to Fla. and Tex. ; Guatemala. 



4. SALVINIACEAE Reich. Salvinia Family 



1. AZOLLA Lam. 



1. Azolla caroliniana Willd. Water Fern. Map 42. This species is 

 found in stagnant water along streams, about lakes, and in dredged ditches. 

 It is doubtless much more frequent than our map indicates. I did not know 

 the species until recent years and I suspect that many collectors are not 

 acquainted with it. It is usually found associated with duckweeds. This 

 species was first reported from Indiana by Prince Maximilian in 1839. It 

 has been reported so far from Starke and St. Joseph Counties. 



Mass., Ont. to B. C, southw. to Fla., Ariz., and Mex. ; also in tropical 

 Amer. 



5. EQUISETACEAE Michx. Horsetail Family 



1. EQUISETUM [Tourn.] L. 



[Schaffner. How to distinguish the North American species of Equis- 

 etum. Amer. Fern Jour. 13: 33-40; 67-72. 1923. Diagnostic key to the 

 species of Equisetum. Amer. Fern Jour. 22 : 69-75 ; 122-128. 1932.] 



J. H. Schaffner, our foremost authority on the genus Equisetum, has 

 seen and named all of my specimens. The following key has, for the most 

 part, been adapted from Schaff ner's keys. 



Stems without or with little chlorophyll, unbranched at first or permanently so, always 

 terminating in a blunt cone. 

 Sheaths bright reddish brown and translucent, their teeth comparatively long, 

 cohering in 3 or 4 broad lobes; fertile stems finally developing whorls of com- 

 pound green branches; internodal ridges sometimes with rows of siliceous 



spinules. (See excluded species no. 13, p. 1021.) E. sylvaticum. 



Sheaths not reddish brown and translucent, their teeth not cohering in 3 or 4 broad 



lobes. 



Teeth of the sheaths light brown, membranous, usually soon becoming green; stems 



soon developing whorls of 3-angled, green branches, with deltoid, membranous 



teeth; internodal ridges sometimes with rows of spinules. (See excluded 



species no. 14, p. 1021.) E. pratense. 



Teeth of the sheaths dark brown, rigid, only slightly membranous at the margins ; 

 stems withering promptly after the spores are shed; sheaths rarely slightly 



green; internodal ridges without spinules 1. E. arvense. 



Stems green or with green branches, with or without cones. 



Teeth of the lower sheaths of the main stem cohering in 3 or 4 broad lobes, com- 

 paratively long, bright reddish brown, and translucent, not deciduous; branches 

 of the whorls prominently compound, horizontal or often curving downward, 

 especially on the fertile shoots; stomata in bands; internodal ridges with or 

 without 2 rows of siliceous spinules; cones not apiculate. (See excluded 



species no. 13, p. 1021.) E. sylvaticum. 



Teeth of the sheaths of the main stem neither united in 3 or 4 broad lobes nor bright 

 reddish brown, deciduous or persistent. 



