OLIVER OK THE STEM OF DICOTYLEDOKS. 251 
other hand, the part in question is entirely ossified, forms the 
spongy ethmoid, and consists of a middle part, the nasal septum, 
higher than it is thick, and of the almost pyramidal lateral parts, 
with their bases directed forward, and coalescent with the median 
part throughout almost their entire length. Each, when it is united 
with the median part, exhibits a short, but perfect, longitudinal canal 
for the passage of an olfactory nerve. Just below the middle part 
of the ethmoid lies the vomer. As is the case, it seems, in most osseous 
fishes, the coalesced part of the trabeculae cranii, together with its 
lateral processes, either ossifies entirely or for the most part, and 
then forms a special ethmoid, which now imperfectly closes the cranial 
cavity in front. In the Pike, however, it persists in the cartila¬ 
ginous condition, for only a relatively small bony nucleus is 
developed in its two lateral processes, and in the two small lateral 
cornua of its anterior end. 
{To be continued .) 
XXII.— The Structure of the Stem ik Dicotyledoks ; beiko 
Keferekces to the Literature of the Subject. By Pro¬ 
fessor Oliver, E.L.S. 
( Concluded from N. H. i?., April, 1862, page 329.j 
Piperaceae. Moldenhauer, J, P. Beitrage z. Anatomie der Pflanzen. 
Kiel. 1812, p. 5, in note. An absence ^of pith and medullary 
rays in some species.—Duvernoy. IJntersuch. fiber Keimung, 
&c. d. Monocotyl. 23, tab. i.—Kunth, C. Sur le genre Piper , 
&c. Mem. du Museum. 1818, iv. 442.—Meyer, E. H. E. De 
Houttuynia atque Sanrureis. 1827, p. 38, fig. 5-9.—Blume, C. 
L. Obs. sur la Structure des Poivres. Ann. Sc. Hat. 1827, 
216. (Ext. Mem. Soc. Sc. Batavia, xi.)—BischofF, Lehrbuch, ii. 
63.—Treviranus, L. C. Physiol, d. Grewachse, i. 210.—Meyen, 
E. J. E. Pflanzen-Physiologie, i. 332. In the young stems of 
Piperaceae the vascular bundles are irregularly scattered, as 
also in herbaceous species, in which this arrangement obtains 
throughout the duration of the stem. In the ligneous species 
a regular closed ring of wood forms in the second year’s shoots, 
enclosing the parenchym, in which the first-formed bundles 
are isolated. The wood zone increases in breadth with age. 
•—Miquel, E. A. W. Commentarii Phytographici. 1838-40. 
On the structure of the stem, p. 3 .—Tiper rubricaule. Link. 
H. E. leones Anat. Bot. 1837, fasc. ii. ix. 9-10.—Kunth, C. 
Bemerkungen fiber d. Eamilie der Piperaceen. Linnsea, 1839, 
xiii. 561. Ann. Sc. Hat. Ser. ii. xiv, 173. Peperomia. The stem, 
composed of separate ligneous fascicles, presents a Monocotyle- 
donous structure. In arborescent and frutescent Piperaceae 
the wood is compact, in layers, and separated by large medullary 
