134 Hhodora [July 



variety is darker colored in all its parts and more compact than is 

 the species, suggesting a more xerophytic plant. The perichaetial 

 leaves, although usually more conspicuous and more prominently 

 hyaline, are not necessarily any larger than in the species. This 

 variety undoubtedly occurs in Vermont though no record of its occur- 

 rence there has been found. 



The var. uliginosum is just such u variation as might be expected 

 in a very moist, well shaded, and humid situation; that is, with 

 elongated and more or less flexuose stems, longer and more distant 

 leaves. In the dried state a very pronounced character is the abruptly 

 squarrose upper portion of the leaf, the apex of which is often some- 

 what recurved or even circinate. It should be expected in all the 

 New England states. 



From an examination of some thousands of leaf sections of P. 

 commune and its allies during the past year it is quite evident that there 

 is much more variation in the lamellae than might be exjK'ctcd from 

 reading standard descriptions; for instance, the end cells in sections 

 may vary from strongly crescentic to circular in the same leaf, depen<l- 

 ing respectively upon whether the section is cut near the middle of 

 the leaf or down near the sheath. likewise, the heights of the lamellae 

 vary. Again, the lamellae of immature leaves differ from those of 

 mature ones. The leaves and lamellae of new shoots differ from 

 those of the old shoots when the amount of humidity or soil moisture 

 is altered. This can easily be shown experimentally by transferring 

 a plant from a moderately dry situation to a dish of water under a 

 bell jar and later com))aring the leaves of the new shoots with those 

 of the old. The thickness of the outer wall of the end cell is also a 

 variable quantity. In fact it is quite evident that certain external 

 factors (climatic and edaphic as well as physiographic) play no small 

 part in determining the form and structure of the lamellae, the leaves, 

 and even the whole plant. The query suggests itself, "Are these 

 factors alone wholly responsible for the existence of any of the varieties 

 which have received distinctive names?" Here is a good field for 

 ^experimentation . 



Polytnchum formomm was re])orted from various New England 

 states prior to 1885. Undoubtedly the bulk of the material so re- 

 ported must be referred to P. Ohinense as has been repeatedly shown 

 in various articles and catalogues since the date mentioned. 



Polytrichum gracile was reported from Massachusetts and New 



