GBEENE — ITKLKA IN THE WEST AM» BOUTHWEST. OJ 



their twigs of one year's growth; and of actually supreme taxonomic 

 importance in the case of the oaks are the color, texture, duration, 

 marginal indentation, and pubescence of the leaves. Not even the 

 characteristics of the acorns are found to be of equal weight with the 



mere hue and texture of foliage in the classification of the oaks. And 

 all this I find true in regard to Ptelea, and even more; for the charac- 

 teristics of twigs of one season's growth in this genus, their colors, 

 kinds, and degrees of pubescence, evenness and unevenness of sur- 

 face, etc., are many times more diverse than they arc in any oak-: 

 and both those sets of characters- those furnished by the twigs and 

 those presented by color and texture of foliage cither set indispen- 

 sable to any natural arrangement of Ptelea species, are here tor the 

 first time brought to notice. The chaos that has reigned hitherto in 

 respect to Ptelea of the farther West and Southwest has held sway 

 because it has not been seen that, in the species of one region, the 

 twigs are chestnut-brown and velvety in one set, chestnut-brown and 

 smooth and shining in another set; while in another and remoter dis- 

 trict all the species have cinnamon-red warty twigs; and in a third 

 croup the twigs in all the species are either yellowish or straw-colored 

 or nearly white and in almost all smooth and shining. 1 say with con- 

 fidence that these marked diversities which even the dead and dry 

 herbarium specimens exhibit can not have been looked at: for no 

 botanist would pretend that one species of shrub or tree could so vary 

 in respect to the bark of it- twigs and branches. 



The fruits in this genus are also found to present a considerable 

 array of characters available for specific diagnosis, and also even for 

 the grouping of the species: and some new descriptive term- have 

 seemed to be called for in connection with them. The body n( the 

 samara, while in the broad, thin- leaved specie- it i- thin and rather 

 flat as well as small in proportion to the wing, i- by comparison large 

 and double-convex as well as more narrowly winged in the species 

 that have a thick and subcoriaceous foliage. This seed-bearing body 

 is in some marked by rather closely parallel transverse ridges, with 

 lines of gland dots running between them, or else the ridges are irreg- 

 ularly broken and run into a reticulation, with one or more dot- in tin 1 

 middle of each mesh. In either instance the ridges may, at the edge 

 of the body or a little beyond it. unite to form a vail more or less 

 definitely surrounding the body — which wall I denominate the circum- 

 vallation — or they may pa-- directly into the reticulation of the wing 

 it-elf. Leaving the body without circumvallation. 



In the Californian group of species the ridges o( the bodj ^\ the 

 fruit are mostly faint or obsolete, in which case the eland dot- are 

 multiplied and very conspicuous, m the Lower Californian nearly or 

 quite wingless species rising into a prominent tube rculat ion. Again, 

 and with respect to it- proximity to either the base or the summit of 



32966—06 2 



