THE AMPHIBIOUS QUILLWORTS. 



HE aquatic quilhvorts are naturally 

 found in lakes and ponds, since few 

 other situations present the unvary- 

 ing water-level and other conditions 

 favourable to their growth. The 

 amphibious quilhvorts, on the con- 

 trary, are more frequently to be found along rivers and 

 streams where the receding waters leave them exposed 

 to the air for at least a part of the summer. The few 

 members of this group that grow in lakes and ponds are 

 to be found close to the margin, in which situations they 

 are usually above the water for a part of the summer at 

 least. 



Engelmanns i^uillwort. 



Among American students of the Isoetes there are few 

 whose names are more closely associated with the genus 

 than that of the late Dr. George Engelmann, of St. 

 Louis, and it is most fitting, therefore, that the species, 

 Isoetes Engelmanni, which commemorates his name, 

 should be both common and widely distributed. 



This species may at once be distinguished from the 

 aquatic quilhvorts by its much longer leaves. In the 

 quiet waters of lake and pond the leaves of the quill- 

 worts are inclined to be short and arranged in a distinct 



