i82 THE AZOLLAS. 



As they float on the surface of quiet pools their resem- 

 blance to small green and red snow flakes is more than 

 an idle fancy. From the stems slender rootlets go 

 down into the water, and should it happen that the. plant 

 is stranded by reason 'of the lessening of the pools in 

 summer, the rootlets are able to strike into the mud 

 and so continue the existence of the 

 plant. There is some reason for be- 

 lieving that the differences in the 

 colour of the fronds are due to differ- 

 ences in habitat, those growing on the 

 water in full sun being usually tinged 

 with red, while those that root in the 

 Azoiia caroiiniana. ud are nearly always deep green. 



(Enlarged.) This Species is Supposed to be 311 



annual, but the author has found it, though in lessened 

 numbers, in mid-winter in New Orleans, often in pools 

 liable to have a thin coating of ice. It develops very 

 rapidly with the return of warm weather, and by mid- 

 April the pools back of the levees along the lower 

 Mississippi are entirely covered by it. Some idea of its 

 possibilities of growth may be gained from a note by 

 Prof. R. S. Cocks, in the Fern Bulletin for 1904, in 

 which he says that in Audubon Park, New Orleans, 

 between the months of June and September, there was 

 removed from the surface of a pond about a quarter of 

 an acre in extent no less than fourteen cartloads of this 

 plant, with a total weight of seven tons. 



The sporocarps are borne in the axils of the leaves, 

 and in addition to the spore-cases nearly always contain 

 the resting bodies of a certain alga (Analnena azolhc.} 

 As soon as the spores begin to gerfninate, these resting 

 bodies of the alga do the same, and as soon as the 



