12 MISC. PUBLICATION 4 7 7, U. S. DEPT. OF AGRICULTURE 



in a warty appearance as opposed to the regularly thickened scales of 

 Lepidobalanus. A few species of Erythrobalanus have the cup scales 

 actually thickened basally. In some species of Lepidobalanus the 

 mature cups are inflated and the margins inrolled against the acorn. 

 Occasionally the margins are very minutely inrolled without any evi- 

 dence of inflation of the cups. In others the cup flares out as though 

 it were dehiscing so that the entire structure becomes a disk. All 

 these characters must be treated with extreme care, for degree of 

 maturity is often distinctly a function of these variations. Only the 

 form of the scales seems to remain relativelv constant within a species. 

 (See pi. 3.) 



Another character of the cup is the degree of inclusion of the acorn 

 at maturity. This normally varies within the genus from completely 

 covered acorns to those included at the base only. In the Central 

 American flora very few species occur with acorns more than about 

 two-thirds included. This character also is a function of maturity 

 and should be regarded with considerable suspicion unless a large 

 series of fully mature fruit is available. For instance, several of the 

 synonyms of Q. corrugata arose through the description of perfectly 

 mature fruits of that species, the species previously having been known 

 only from immature specimens. Furthermore, the character is not 

 necessarily a constant one even if fully mature fruit is available in 

 abundance. The several clearly conspecific forms of Q. pilicaulis 

 have cups and acorns which differ widely and in a most haphazard 

 manner. The fruiting characters in this case must be held secondary 

 to the more fundamental of the several vegetative characters. 



METHODS 



Aside from the consideration of the anatomical characters of the 

 wood, a study that was carried on concurrently with this one, no 

 innovations have been introduced in the taxonomic procedure. The 

 complete aggregation of specimens here cited was gathered together at 

 one time and studied as a single collection over a period of several 

 months. This method served to avoid many errors and much lost 

 effort such as one experiences in studying first one collection, then a 

 second, and finally attempting to correlate with these a third. 



Since Trelease's monograph contains photographs of the types of 

 nearly all the species then known, no special effort was made to 

 choose types for the illustration of this publication except in the case of 

 new species or those published subsequent to Trelease's volume. The 

 policy followed was rather to select the most representative specimens 

 and those most illustrative of common variations, relationships, dis- 

 tinctive characters, etc. The illustrations are meant to serve less as a 

 record than as a supplement to the key in the identification of species. 



If the type or an isotype of a species is cited under specimens ex- 

 amined, it is not mentioned elsewhere. Otherwise, the type is desig- 

 nated following the data on the range of each species. 



