546 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
they contain much less chlorophyll. In the stronger bundles the cells 
of the sheath may be found on both sides of the bundle, or they may be 
replaced on both sides or on the under side only by the parenchyme of 
the bundle. In the second type, which occurs in the Chenopodiacese, 
Amaranthaceae, and Portulacacese, the cells of the sheath are of a cubical 
or bluntly pyramidal form, and are arranged in a distinctly wreath-like 
manner. They are never separated by intercellular spaces. Their walls 
are very thick, and they contain a considerable number of large chloro- 
phyll grains. 
Staminal Vascular Bundles.* — M. P. Grelot points out that it is 
not at all an uncommon phenomenon for the vascular bundles to undergo 
great degradation or even to disappear entirely in the stamens, even in 
orders which are considered high in the scale of development. This 
degradation is first manifested by a reduction in the number of 
spiral and annular vessels in the xylem; while in other cases the 
thickening-bands have entirely disappeared. The phloem-portion of the 
bundle is always much more fully developed than the xylem-portion. 
This degradation is strikingly exhibited in Myosotis. The principal 
function of the vascular bundles in the floral organs appears to be the 
transport of dissolved nutrient substances, and this takes place chiefly 
through the phloem. Where the organ is but temporary, as is the case 
with many stamens, there is no need for xylem. 
Polystelic Boots of Palms.j — Mr. B. G. Cormack calls attention t«> 
the general sameness in the form and structure of the root in vascular 
plants. But in Areca Catechu , instead of the normal central stele of 
small diameter, four other types may be recognised, passing into one 
another by insensible gradations ; and a similar variation was observed 
also in other species of palm. Aerial roots are not infrequently poly- 
stelic in their thicker older parts ; and this difference in structure is due 
to a continuous change in the mode of differentiation of the apical 
meristem. The whole structure of the older aerial parts is such as to fit 
them for withstanding both pressure as props and tension as stays ; while 
the thinner subterranean parts are normal in conformity with the nor- 
mality of their functions and environment. In correlation with the bulk 
of these roots and the absence from them of pneumatodes, there is a 
conspicuous formation of pneumatophores. 
Wood of Pomeae and Amygdaleae.f — Dr. A. Burgerstein continues 
his observations on the structure of the wood of the Pomeae. On histo- 
logical grounds he advocates the retaining of Cotoneaster as a distinct 
genus, with which Pyracantha should not be associated. Mespilus also 
should not be united with Cratsegus. He enters into further details with 
respect to the structure of the wood of the Amygdaleae ( Prunus ), which 
differs from that of the Pomeae in no essential respect, though there are 
minor points, especially in the size of the vessels. 
Stem of the Sugar-Cane.§ — Herr A. Wielerhas examined the struc- 
ture of the stem in a number of different varieties of the sugar-cane, 
* Rev. Ge'n. de Bot. (Bonnier), ix. (1897) pp. 273-81. 
t Trans. Linn. Soc., v. (1896) pp. 275-86 (2 pis.). 
X SB. K. Akad. Wiss. Wien, cv. (1897) pp. 552-82. Cf. this Journal, 1896, 
p. 642. § Beitr. z. wiss. Bot. (Funfstiick), ii. (1897) pp. 141-65 (2 pis.). 
