THE CENTRAL AMERICAN SPECIES OF QUERCUS 11 



glabrous except for small tufts of tomentum in which are embedded 

 the abortive ovules. These tufts are related rather to the ovules 

 and the integument of the seed to which they adhere than to the 

 acorn shell. In Erythrobalanus, on the other hand, the shell is with- 

 out exception densely and permanently covered with a thick, felt- 

 like layer of matted creamy or silvery tomentum. This is an unfail- 

 ing distinction between the subgenera. 



The cotyledons and radicles of the species of Erythrobalanus and 

 of all but a few species of Lepidobalanus are very constant in their 

 relative positions. The cotyledons are equal in size and similar in 

 shape, and the radicle is in an apical position and apically directed. 

 In the several species comprising the proposed genus Macrobalanus 

 of Schwarz the cotyledons are unequal in length, the radicle lying at 

 the apex of the shorter cotyledon and therefore in a lateral position 

 and obliquely directed. This character is apparently constant for 

 most of the species of this group of which fruit is known, but the 

 recently discovered Q. panamandinaea has cotyledons of both types. 



The involucre or acorn cup consists of a saucer-shaped to deeply 

 cup-shaped structure the outside of which is covered by a spiral series 

 of imbricate scales. Trelease (6, pp. 8-10) calls attention to what he 

 terms " acornlike galls", which occur occasionally in the axils of the 

 cup scales. He also mentions the rare replacement of the scales by 

 leaves as evidence of their foliar origin, which he says lends indirect 

 support to the belief that the acorn cup is "constituted by the fused 

 secondary branches of a dichasium." Whether the inflorescence 

 from which the cup is derived be a dichasium or of some other type 

 is not clearly indicated by the teratology of the cup. The spiral 

 arrangement of the scales, which is clearly evident in certain loosely 

 formed cups such as those of Q. humboldtii, might as readily indicate 

 the cup to be a contracted spike. This would bring the pistillate 

 prototype nearer the author's present conception of the staminate 

 inflorescence. 



At the same time the occurrence of several cups on a single peduncle 

 would suggest origin from a compound inflorescence. The very com- 

 pact fruiting peduncles of several Asiatic species, which simulate a 

 cone with numerous acorns embedded in a matrix of barely distinguish- 

 able cups, is very strongly suggested in a teratological specimen of 

 Q. humboldtii (Bro. Thomas 766). In this the scales of the cups are 

 not only foliar in nature but each bears in its axil a perfectly formed 

 pistillate flower seated in its own small cup. This may be interpreted 

 as meaning that each cup scale is fitted with a reduced and normally 

 nonfunctional bud in its axil, which represents an obsolete branch of a 

 formerly compound inflorescence. 



The acorn cups of Quercus offer some very valuable characters for 

 the distinction of groups of species. The subgenus Lepidobalanus is 

 characterized by scales which are loosely appressed, rather pointed 

 at the apex, and more or less keeled or corky-thickened at the base. 

 Those of Erythrobalanus are characteristically thin and closely ap- 

 pressed, blunt or rounded at the apex, and not thickened or keeled 

 basally. Certain groups of species in Erythrobalanus that are other- 

 wise orthodox have loosely appressed scales, and certain others 

 frequently show an apparent basal thickening that is actually a 

 partial development of the axillary buds beneath the scales and results 



