sporanges with normal ones, I think them explainable better on the 

 theory of accidental variation, than on that of hybridity, especially 

 as they are found where the species do not grew in juxtaposition. 

 My investigations on this point have been extensive, covering 

 thousands of plants, and my conclusion is that hybridity in this 

 genus, though not impossible, nor even improbable so far as ex- 

 ternals go, is at least extremely rare among New England species. 



I wish here to pay tribute to the general excellence of Mr. 

 Dodge's treatment of the genus, a more practical account never 

 having been written ; and for the beginner, I can conceive of no bet- 

 ter directions than are contained in his notes. I wish I could say 

 as much for Britton and Brown's more pretentious "Illustrated 

 Flora," but to anyone with more than the most superficial knowl- 

 edge of the genus, their treatment is very disappointing. 



Considerable labor has been expended by Durieu, Braun, and 

 Engelmann, to devise some system of classification that would hold 

 water, but with ill success, as they themselves testify ; for while it 

 is comparatively easy to classify species of a limited area, the sys- 

 tem fails when applied to the genus as a whole. Perhaps the most 

 natural grouping is into the three divisions Aquaticae or Submersae, 

 Amphibiae, and Terrestres, and if applied with sufficient looseness 

 will hold. But Submersae in Europe are bilobed and without 

 stomata, consisting of the species lacustris and echinospora. When 

 applied to the genus as a whole, however, we find Gunnii and elatior 

 of Tasmania three lobed, and also find our varieties of echinospora 

 with stomata, thus placing them in a different group from the type, 

 as indeed they appear from habit to fall. The system fails, too, 

 when taken in its original sense in the division Amphibiae. All 

 Old World species of this group are three lobed, and this was made 

 use of in the classification ; but not one of our numerous species of 

 eastern America is three lobed, and only four from North America, 

 Nuttallii, Cubana, Orcuttii and minima, are so constituted. The 

 only works treating of the genus as a whole, do not tend to clear 

 up the matter. Baker, in "Fern Allies," treats the genus very 

 superficially, while Motelay's more pretentious work is full of inac- 

 curacies, nearly two pages being given to " errata," and these cov- 

 ering a small percentage of those contained in the work. Though 

 a help in many ways, the critical student hesitates to place much 

 weight on statements accompanied by such errors. 



The group Terrestres is, it seems to me, unnecessarily limited 

 to the two species with persistent leaf bases. Nuttallii, fiutleri, and 



