84 Chronicles of Science. [Jan., 
usually supposed to be reservoirs of air. These liquids, however, 
being perfectly clear, may be ordinarily invisible; moreover, when 
separated from the plant, air would readily find its way into them. 
He maintains that there is no proof that trachez are exclusively 
tubes for the conduction of gases. In their youngest condition 
the trachean vessels are found to be full of fluid, like the other 
elementary organs, though this fluid appears to be lost at a more 
advanced stage. He believes, however, that they are still tra- 
versed by denser liquids, and his observations go to prove that 
these liquids may become so much thickened as ultimately to fill 
up the cavity and obstruct the circulation. ‘Thus, in the stem of 
the Rotang he found that the great vessel occupying the centre of 
most of the bundles was filled with a solid white material, with 
cylindrical masses sometimes continued, sometimes broken up, and 
which broke up into granules when immersed in water, the granules 
having a very active movement, although the vascular tissue had 
long been dried up. In a vine stem also, cut into short pieces, a 
transparent matter of the consistence of gum was found to exude 
in abundance from the cut surfaces in a very short time. Smaller 
sections being cut, he found the next day that in the mean time 
gummy filaments had protruded from the large vessels, from which 
he infers that the trachex, even in old plants, contain matters of 
considerable density as well as the aériform substances which are 
usually considered to Le their sole contents. 
M. Caspary describes an organ in plants which he terms the 
protective sheath, consisting of a layer of very closely approximated 
cells placed in a single series in thickness. which protects the 
vascular system of the stem, roots, and leaves.. In some cases, 
however (as in Berberis), this layer is ruptured during its growth, 
and consequently does not serve to protect the organs which it 
envelopes. He observes certain folds upon the cell walls of the 
protective sheath of Ficaria ranunculoides, &., which at first 
appeared to be pores, but when the cells of the protective sheath 
become thickened these folds gradually disappear, a change which 
he attributes to the elongation of the walls of the cells. This 
protective sheath has been regarded by M. Karsten as a lignified 
residue of the layer of cambium, which has produced the other 
parts of the stem ; but M. Caspary controverts this, and also main- 
tains that the entire terminal bud is formed of cambium, and 
already contains the mother-cells of all other kinds of tissue which 
will subsequently form the various parts of the stem, against the 
opinion which derives all the parts of the stem from a single layer 
of cambium existing in the terminal bud. (For an abstract of 
his paper, see ‘Annals Nat. Hist.’) 
Tn the ‘Comptes Rendus’ M. Fournier makes some observations 
