62 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
intercalary to internal or external by the folding of the arc. The mode 
in which these variations and complications take place is often charac- 
teristic of natural families. 
Cuttings of the Vine.* * * § — According to M. L. Bavaz, at the point 
where a cutting of the vine puts out a root, the generative layer becomes 
more active over a space of 4-5 mm. diameter, and forms xylem inter- 
nally, phloem externally, the root originating in the outermost layer of 
cells of the phloem. The “ digestive pocket ” is formed at the expense 
of the innermost layer of the medullary ray of the preceding year. In 
order to make its exit, the root has to penetrate the phloem of the pre- 
ceding year and a layer of bark, and consumes in its progress a very 
spongy and thin- walled tissue formed from the innermost layer of 
the corky envelope of the fibrovascular ring. This takes place in nearly 
all the varieties of the vine examined. Decortication facilitates the 
rooting of the cutting, but only by promoting the penetration of water 
into its tissues. 
Cystoliths.j — Dr. L. Eadlkofer describes the various forms of cysto- 
liths and the cells in which they are contained. The natural orders in 
which their presence has been certainly determined amount to 10, viz. : 
— the Urticace®, Acanthaceae, Cucurbitace®, Begoniaceae, Gyrocarpeae, 
Olacineae, Cordiaceae, Borragineae, Hydrophyllaceae, and Verbenaceae. 
In addition to ordinary lithocysts, the cystolith may be developed in 
hairs with moderately thick walls and superficial calcareous deposits, 
which are frequently collected into rosettes. 
Mestome- sheath of Grasses.}: — Herr S. Schwendener finds that in 
the leaves of Gramine® the mestome-bundle is usually inclosed in a 
typical protecting sheath, and that its formation is not dependent on 
external conditions ; but that it can be used, to a large extent, as a taxo- 
nomic character. The cells of this sheath are parenchymatous, often 
with sharpened ends ; their walls have roundish or oval pores, and the 
thickening is usually on the inner side. It frequently, in the smaller 
bundles, completely surrounds the sieve-portion only. Whether this 
mestome-sheath is present or not, each separate bundle in the leaves of 
grasses is surrounded by a parenchymatous sheath. 
A similar sheath occurs also in some other natural orders, as in the 
Stachyde® among Labiat® (it is wanting in the Ocymoide®). It is 
almost invariably present in underground stems, even when entirely 
wanting in the aerial organs. 
Mucilage and other glands of the PlumbagineaeJ — Mr. J. Wilson 
in the first place draws a distinction between the two sets of secreting 
organs, viz. the Mettenian glands, characterized by the secretion of 
calcium carbonate, which are universally distributed over the vegetative 
organs, and the mucilage-glands, which are confined to the axillary 
regions. Glands displaying every stage of gradation from the one 
form to the other are, however, met with in abundance ; there can be 
no doubt that both sets of glands have the same origin, and it is 
* Comptes Rendus, cxi. (1890) pp. 426-8. 
t SB. K. Bayer. Akad. Wiss. Miinchen, 1890, pp. 115-27. 
% SB. K. Preuss. Akad. Wiss., xxii. (1890) pp. 405-26 (1 pi.). 
§ Ann. of Bot., iv. (1890) pp. 231-58 (4 pis.). 
