THE CENTRAL AMERICAN SPECIES OF QUERCUS 7 



little it may be worth. This character must be used with extreme 

 caution, since fluting is sometimes brought about by the shrinking of 

 very young twigs upon drying. 



The nature and persistence of the pubescence of twigs in many cases 

 are characters of great use in distinguishing closely related or merely 

 similar species. Only rather extreme differences may be relied upon, 

 however, and these are best employed only when several specimens 

 are available to serve as a check upon the constancy of the character 

 in that individual case. Less frequently useful is the presence and 

 conspicuousness of lenticels. Rarely in Lepidobalanus but somewhat 

 more commonly in Erythrobalanus, the presence of numerous and very 

 conspicuous lenticels may serve to distinguish two rather similar 

 species. Rare though the instances are, the character is a relatively 

 constant one within the species. 



Buds. — No characters of profound importance are found in the buds 

 of Quercus, but differences between species are often quite evident. 

 Bud characters are more reliable in deciduous species than in evergreen 

 ones, and they are more evident in temperate areas than in the 

 Tropics. Immature buds may be very misleading, and it is often 

 impossible to find mature buds on evergreen tropical species. The 

 size of the terminal bud is often of diagnostic value, but this character 

 may vary with the degree of vigor of the shoot, the maturity of the 

 bud, and, toward the beginning of the growing season, the swelling of 

 the bud. Shape is a more reliable character except insofar as it too 

 may be affected by growth. However, both size and shape may be 

 used to excellent advantage by choosing the most normal buds avail- 

 able. Pubescence, although less frequently presenting striking and 

 representative differences, is fairly reliable when it is encountered. 



Stipules. — The stipules are of several more or less intergrading 

 kinds. Associated with the lateral buds are pairs of ligulate stipules 

 that in most cases are early caducous but that in a few species are 

 constantly persistent. These are inserted one on each side of the bud. 

 In their axils and lying between them and the bud is a second pair, 

 usually shorter and more persistent and characterized by a broadened 

 base and a somewhat subulate apex. This category of stipules is 

 seldom if ever diagnostic and is not included in descriptions. The 

 third class is comprised of the pairs of subulate appendages associated 

 with the terminal buds and often the uppermost lateral (or alternate 

 terminal) buds. These are more frequently persistent than the others 

 and are the ones alluded to in the descriptions unless the lateral or 

 ligulate stipules are specifically mentioned. 



Leaves. — The most valuable characters in Quercus for distinguish- 

 ing all classes of categories from subgenera to species are found in the 

 leaves. Some of these are only superficial whereas others are very 

 fundamental, but each may be quite readily evaluated. 



The persistence of leaves is in many cases very useful. Those species 

 that clearly indicate an evergreen habit or a deciduous habit are 

 frequently distinguished from one another on this basis. However, 

 the habit is not always apparent, because the old leaves may drop 

 very shortly after the young ones unfold and because occasionally 

 a deciduous species may undergo renewal of growth toward the end of 

 the growing season, which gives the appearance of an evergreen habit. 

 The character, therefore, is too difficult to apply and too inconstant 



