556 Robinson: Polycodium 



In the Vaccinium group as a whole there is a transition in this 

 'espect, and Polycodium is merely one case of many. In certain 

 species, such as V. caespitosum Michx., V. scoparium Rydb., and 

 V. Myrtillus L., the flowers are few in number on a branch borne 

 in the axils of what are apparently quite normal leaves as to size, 

 shape, and texture. In others the inflorescence is quite clearly 

 racemose, or by contraction fasciculate, the pedicels subtended 

 by bracteoles quite different in appearance from the vegetative 

 leaves. This includes nearly all the species of the eastern United 

 States. There is yet a third group, which almost perfectly links 

 the two r the inflorescence being perhaps best described as a leafy 

 raceme. These are mostly tropical plants. Incidentally, these 

 three groups follow rather closely the lines indicated by the 

 stamens. 



In the case of Polycodium there is a group "in which," to use 

 Nuttall's expression* when describing Picrococcus floridanus, "the 

 flowers appear truly axillar." Here also belong the names Polyco- 

 dium caesium Greene, P. oliganthum Greene, and P. revolutum 

 Greene. Nuttall's type seems to have perished, which will cause 

 trouble to those who believe this group to contain more than one 

 species, for he has no sufficient description for more definite deter- 

 mination. In the case of the other species duplicates of the type 

 collections have been examined, and there seems no sufficient reason 

 for holding them distinct. In separating P. revolutum from P. 

 caesium Professor Greenef relies chiefly on the leaves of the former 

 being more pubescent, more oval and obtuse, their margins 

 revolute, the calyx lobes deeper, acute or acuminate instead of 

 scarcely acute, and deeper corolla lobes. It is not possible to 

 separate the series of specimens on these characters or any of them, 

 those drawn from the leaves being especially unreliable, not even 

 holding for the collections on which the species were based. There 

 seems even less reason for segregating P. oliganthum. 



Now, the same thing happens in Polycodium as in the Vac- 

 cinium group in general; the leaves, in the axils of which the 

 flowers are borne, are often reduced in size but still retain the other 

 characters of the typical leaves of the plant; yet again, they may 



* Trans. Am. Philos. Soc. II. 8: 262. 1843. 

 tPittonia3: 249,250. 1897. 



