250 
CONTRIBUTIONS TO BOTANY. 
border in that tribe, as in others of the Rhamnacea, have a 
prominent keel along the middle of their internal faee, which 
terminates below the apex in an elevated callous gland, con- 
nected with two other raised lines that run along the border. 
These medial keels and glands have been supposed by some to 
be so many sterile stamens ; but Brongniart, with more truth, 
considers their appearance to be the result of the impression 
left upon the soft fleshy lobes of the calyx, while in {estivation, 
by the indentation of the enclosed petals and stamens ; that 
such is the real cause, is shown in the instance of Gouania, 
where a similar carinal prominence exists in the calycine lobes, 
and, in addition, at the base of each keel is seen an acute scale, 
which is really the rudiment of an abortive stamen. Similar 
impressions are frequent in many other families where the floral 
envelopes have a valvate aestivation. We meet with another 
point of structure in the Colletiece, which, as far as I am aware, 
bas not been noticed by botanists : I refer to the peculiar deve- 
lopment of the stipules. Brongniart, who enters fully into detail 
respecting the several parts of the plant in the Rhamnacea, in 
describing their stipules, does not allude to it; he even states 
that these organs are entirely wanting in Retanilla, where I find 
this development to be a very characteristic feature. Beneath 
each spine and at the base of each petiole, a dark red-coloured 
broad scale is seen, which somewhat embraces the stem ; it is 
concave, and terminates at the apex in two short teeth, or 
lengthened erect linear segments, the petiole appearing to spring 
from between them : in some instances, as in Colletia, Talguenea, 
Trevoa, Adolphia, and Scypharia, these stipular scales are simply 
amplexicaul ; but in other cases, as in Notophoena, Retanilla, 
Ochetophila, and Discaria, those of the opposite axils unite in a 
short vaginal sheath, forming a dark transverse line around the 
stem, making each node seem to be articulated, as in Ephedra. 
Between each scale and its corresponding spine, a tubercular 
swelling originates, upon which both leaves and flowers appear, 
when, as frequently occurs, they are fasciculated : this tubercle 
is, in fact, a suppressed or undeveloped branchlet ; the scales 
are the opposite stipules of the approximated decussating axils, 
some of which are sterile, while others produce both leaves and 
flowers, or each separately. This feature affords a very good 
discriminating character in some of the genera. 
After these prefatory remarks, I proceed to the consideration, 
in succession, of the sevei'al genera of the Colletiece, separating 
the tribe into three divisions : — 1, where the petals are wanting, 
and the fruit is separable into distinct cocci ; 2, where petals are 
present, with a similar fruit ; 3, where petals are also present, 
but where the fi-uit is indehiscent. 
