in the Brontes and their Brown Rust . 305 
ness of the cell-walls, cuticle, waxy bloom, &c., were obtained, 
and these factors are omitted from the Tables. 
12 . General Anatomy of the First Green Leaf. 
In all the species examined the first green leaf of the 
seedling is ligulate, acute, and slightly hooded at the apex, 
varying in length from 40-50 to 80-100 mms. and inrolled 
at the base. The length is not sufficiently constant to be 
of service as a character, but the breadth, from 1-3 mms., is 
remarkably so, as the table of measurements shows. 
The mid-rib always contains the strongest vascular bundle, 
and has a keel— which may be very slight however — sub- 
tending it. This is flanked by one, two, or three ribs on each 
side, according to the species, in each of which a weaker 
bundle runs. Thus B. mollis , B. arvensis , B. interruptus , &c., 
have usually three ribs in all, B. secalinus , B. sterilis ) &c., have 
five, while B. maximus , B. unioloides , &c., have seven. It 
appears to be constantly the case also that each alternate rib 
contains a feebler vascular bundle ; for instance, where there 
are three in all, the strong mid-rib is flanked by a weaker one 
on either side ; when five are present, those nearest the 
margins are stronger than those between them and the mid- 
rib ; and when there are seven in all, the second from the 
margin on each side is stronger than those on either side 
of it. 
Corresponding to each rib is a ridge, i. e. the tissue of the 
leaf is thicker especially above (but also below) than in the 
intervals, and we thus have a series of intervening grooves 
alternating with ridges, especially on the upper surface of the 
leaf. It is in the tissue beneath these grooves that the chloro- 
phyll is aggregated. 
It is on the flanks of these ridges, and only there, that the 
stomata occur. These are arranged in longitudinal series, 
usually a single series on each flank of the ridge, but occa- 
sionally double (and, rarely, even triple) on one flank of one 
ridge on each half of the lamina. 
There is no exception, in the cases examined, to the rule 
