140 AMERICAN MIDLAND NATURALIST 
6. RULAC MEXICANA (DC.) 
Negundo mexicanum DC., 1824* 
Acer mexicanum. (D.C.) Pax, 1886, not Acer mexicanum 
A. Gray, 1861. 
This species differs rather notably from all the foregoing 
by its regularly sharply serrulate oval or ovate leaflets. These 
are always trifoliolate and densely silky tomentose beneath. 
It is native of Southern Mexico, and specimens found in 
Guateniala are typical in every way except the larger size of the 
leaflets. 
It seems that the Asiatic group of pinnately trifoliate maple- 
like trees have been confounded with the real American Box- 
elders. They are, however, only like them superficially and in 
appearance. They differ as a matter cf fact as much from the 
members of the genus Iu/ac as they do from Acer itself. The 
leaves are always pinnately trifoliolate but they are andro- 
monoecious and the disk is not obsolete as that of Rulac. The 
number of stamens differs; there are differences in the inflorescence, 
which is terrnhinal, and the flowers are complete. The group is 
at least as deserving, if not more so, of generic rank than Rulac 
>) 
itself, and I propose for it the name Crula. 
Crula nov. gen. 
Arbores andro-monoicae cum foliis pinnatis trifoliolatis: discus 
bene evolutus et crassus extrastaminalis; gemmae perulae interiores 
elongatae: stamina 8 saepissime elongata medio disco inserta vel 
cum disco extra staminibus; petala evoluta, sepala libera; foliola 
minime lobata; anflorescentia in ramulis terminalibus foliosts 
instta; styl’ usque ad basim distinctt, prope ad alas bene divaricati: 
flores praecoces, fertiles spicati, vel racemost, vel corymbosi vel pauct 
umbellate. 
Per Asiam Orientalem dispersa,; Chinam, Coream, Japoniam 
et Mandschuriam. 
The plants differ from Rulac in being andro-monoecious and 
the flowers in terminal clusters. The leaves are always pinnately 
DC. Prodromus. 1. c¢. 
