given rise to these remarks; obliques t when the angle exceeds 90°; 
and so on. 
Having thus attempted to establish the necessary nomenclature, 
we may proceed to shew, as far as our limits will allow us, in what 
way it may be adapted to practice. 
If we view the subject only with reference to the first great 
divisions of the vegetable kingdom, we shall find that the develop¬ 
ment of the veins is always in direct proportion to the dignity of the 
division. Thus, in the lowest tribes. Fungi and Algae, veins do not 
exist; in Musci they appear under the simple form of a more or less 
complete costa; in Filices the costa becomes more perfect, and 
numerous lateral veins are formed, which do not, however, arrange 
themselves under the same laws as obtain in the higher divisions, 
but are all of equal power, and may perhaps be considered as venulae 
propriae. In Monocotyledones, the next in rank to Filices, venae 
primariae are for the first time formed, and are either connected or 
not by means of venulae propriae; but, with the exception of some 
Aroideae, plants of this division possess neither venae arcuatae, venae 
externae, nor venulae marginales, these being developed only in those 
highest tribes of vegetables called Dicotyledones. 
If we consider the peculiarities of venation in a more confined 
sense, we shall find them scarcely less important. True Aroideae are 
distinguishable from other Monocotyledones by the presence of venae 
arcuatae and venulae marginales. In some plants of the same great 
division, both venulae propriae and venulae communes are absent; in 
others, the former only exist; the latter are rarely discoverable. The 
absence of venae arcuatae and externae, and the abundance of venulae 
propriae, give the peculiar character of the leaves of Amentaceae. 
Nearly the same observation may be made upon Dilleniaceae, with 
the exception of Hibbertia and its allies. Myrtaceae are well charac¬ 
terised by the parallelism and straightness of the venae primariae, the 
confluence of all the venae arcuatae into a continuous line parallel 
with the margin of the leaf, and the occasional presence of venae 
externae in the same direction as the venae arcuatae. This observation 
confirms the propriety of excluding Philadelphus from the order, as 
has lately been proposed by Mr. Don, but is also a strong argument 
against the separation of Punica, to which, indeed, other and perhaps 
better objections might be urged. 
