THE AZOLLAS. 183 



Azolla leaves are developed, they creep into the hollow 

 interior through a pore at the base of the larger lobe of 

 the leaf, and there form colonies. These colonies are 

 nearly always found in Azolla leaves. 



Azolla Caroliniana appears to grow naturally as far 

 north as New York, but in the northern part of its 

 range it is never so abundant or so conspicuous as it is 

 nearer the equator. It is found throughout the South 

 and extends to Arizona and Washington. It occurs in 

 the Mississippi valley at least as far north as Iowa, but 

 its northern range is not well defined. Beyond our 

 limits it is found in suitable places as far south as 

 northern Patagonia. It delights especially in still waters 

 and is seldom found in streams. It is easily cultivated 

 in ponds where it does not gr'ow naturally, and has been 

 thus naturalised in many places, one of the best known 

 of which is on Staten Island, New York. 



j4%olla Filiculoides. 



With the exception that Azolla filiculoides is a 

 slightly larger plant than Azolla Caroliniana, it is almost 

 exactly like it to the unaided eye. Study with the lens, 

 however, shows that the branching in the present species 

 is inclined to be pinnate in form and the fronds elon- 

 gated, while in Azolla Caroliniana they are more deltoid 

 in outline. The large lobe of the leaves in Azolla fili- 

 culoides is ovate, while that of the other is rhombic- 

 oblong and obtuse. 



Azolla filiculoides is widely distributed in South 

 America, being most abundant on the Pacific slope, and, 

 according to Baker, is found in the Andes up to an ele- 

 vation of 16,000 feet. Within our limits it extends to 



