2 
CONTRIBUTIONS TO BOTANY. 
Exogens, under the name of Homogens, the leading feature of 
which was then believed to be, that, “instead of their wood 
being formed by zone after zone, season after season, as is the 
case in the great mass of Exogens, they never have more than 
one zone of woody matter, to whatever age they may have 
arrived.^’ This conclusion was, however, soon abandoned, as 
the existence of more zones than one was fully proved. I have 
frequently seen several annular rings in the stems of Menisper- 
macece ; and Gardner found one, in Ceylon, in which he counted 
more than forty distinct concentric zones ; but such instances 
are comparatively rare. It would be needless to detail the 
structure of the wood in this family, as the subject has been 
ably demonstrated by Decaisne and others, and as there is little 
novel information to offer respecting it. 
The leaves in the plants of this order are constantly alternate, 
petioled, and always without stipules ; but in many cases the 
petiole, finally deciduous, is articulated upon a prominent pulvi- 
nate cup, on the upper margin of which, adjoining the stem, is 
seen a budlike process, appearing as if a pair of stipules had 
embraced the cup, and had become agglutinated to it and the 
stem : this must not be confounded with the gemma of a nascent 
branch or flower-stem, which in most instances is supra-axillary. 
In the genus Antizoma, the pulvinate process just mentioned, 
at its articulation with the petiole, is elongated in the form of a 
spur, so that it bears the appearance of a short spine. The 
petiole is often much swollen and tortuous at its base, and, being 
suddenly bent back, it performs the office of a tendril in sup- 
porting the young climbing branches. Its insertion into the 
blade of the leaf is either peltate or palate. In the former case 
the point of union is never quite central, but always moi'e or less 
excentric, sometimes approaching the margin, where the leaf is 
more or less truncated or cordate. The palate insertion, how- 
evei-, is more frequent, when the petiole, at its junction with the 
midrib, often subtends a considerable angle with the plane of 
the leaf, and is commonly much swollen at that extremity by an 
enlargement which the French botanists call a bourrelet. The 
leaves vary greatly in form, substance, and texture, and have 
generally, but not always, three, five, or more nerves springing 
from the point of insertion of the petiole : they are generally 
entire on the margin, but sometimes are sinuous or distinctly 
lobed, more rarely sinuately dentate, or cleft into palmate seg- 
ments, or (in Burasaia) divided into three sessile leaflets on the 
summit of a long petiole. 
The inflorescence varies in different genera, being chiefly 
axillary, with one or several racemes, more or less simple, grow- 
ing from a point a little above the origin of the petiole : the 
