622 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
(2) In certain trees the tigellary region only developes during the first 
year. (3) The tigellary region is a special structure, and is charac- 
terized by (a) the early appearance of hypodermal, cortical, or pericyclic 
cork ; ( b ) a large development of the external parenchymatous zone ; 
(c) absence of differentiation in the external zone of cortex ; ( d ) a great 
reduction or absence of sclerenchyme ; (e) a large development of wood ; 
(/) absence of the parenchymatous circum-medullary zone ; (gr) feeble 
lignification of the ligneous elements ; (A) a reduction in the diameter 
of the pith. (4) From a physiological point of view the terminal shoot 
of an old tree presents no differences from the caulinary region of a tree 
a year old ; the tigellum is always distinguished by the accumulation of 
reserve-material. 
Stem of Cycadeae.* * * § — Graf zu Solms-Laubach finds, in the stem of 
Stangeria, a cone of vascular bundles, which is prolonged upwards into 
a simple cylindrical tube, and the axis of which deviates only slightly 
from the horizontal. A similar structure probably occurs also in the 
stems of other Cycadeae. 
Decortication of the Stems of Calycanthaceae, Melastomaceae, and 
Myrtaceae.t — M. O. Lignier states that the structure of the cork in 
Melastomaceae presents various aspects. When it forms in the epiderm 
it is composed of uniform cells with thin walls. The pericambial cork 
of the Memecyleae is formed of uniform sclerotized cells, whereas the 
cork of the first group of Melastomaceae (comprising the Microlicieae, 
Osbeckieae, and Rhexieae) is stratified when it is pericambial. The 
author confirms many of the observations of M. Douliot,! and also points 
out that the successive layers of cork in the Myrtaceae present a very 
regular stratification. 
Function of the Sieve-portion of Vascular Bundles. § — Herr J. Blass 
argues against the prevalent view that the main purpose of the sieve- 
structures in the phloem of vascular bundles is for the transport of 
albuminoids. His main arguments are derived from the fact that sieve- 
structures do not occur in the part where they would be most required 
for this purpose, viz. in the immediate vicinity of the growing point, 
being never found in the uppermost internode ; from their very small 
number in proportion to the number of vessels ; and from the circum- 
stance that the sieve-pores are frequently almost entirely closed, or the 
passage through them of the albuminoids greatly hindered by large 
accumulations of callus. From an examination of woody and herbaceous 
plants, Herr Blass found that the development of the sieve-structure bears, 
as a general rule, a direct proportion to the development of xvlem, 
being, e. g., almost entirely suppressed in aquatic plants ; and he believes 
that its chief function is to supply a store of food-material for the 
formative cambium, and for the xylem of the vascular bundles, bearing 
the same relation to these portions of the bundle that the starch-sheath 
does to the phloem portion. 
* Bot. Ztg., xliii. (1890) pp. 177-87, 193-9, 209-15, 225-30 (1 pi.), 
t Bull. Soc. Bot. France, xxxvii. (1890) pp. 12-7. 
X Cf. this Journal, 1889, p. 400. 
§ Ber. Deutsch. Bot. Gesell., viii. (1890) pp. 56-00. 
