68 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
as, for example, Saponaria on CEnoihera. For tlie graft to succeed, it is 
not always necessary for the generating layers to be in contact with one 
another. The failure of grafting is often due to the obstacle presented 
by the cell-walls of the graft-plant to the passage of certain nutritive 
substances from the cells of the host to those of the graft. This is 
especially the case with inulin in the Composite. 
Torsions during Growth.* — Herr H. de Vries gives a very detailed 
account of the various kinds of truo torsion (Zwangsdrehungen), as 
well as those of simple torsion in which the axis remains straight, but 
the appendicular organs are more or less twisted, the original phyllotaxis 
remaining unchanged. A very large number of cases of true torsion 
are described, in plants belonging to many orders of Dicotyledones, and 
to Equisetum among Vascular Cryptogams. The various modes are 
classified as follows : — I. Simple torsions (1) of leaves and leaf-stalks, 
(2) of naked stems, (3) of leafy stems, (4) of fasciated stems ; II. Tor- 
sion of trunks; III. Spiral torsions (1) of stems, (2) of roots; IV. Spiral 
arrangement of leaves usually decussate or verticillate (1) without, 
(2) with connation of the bases of the leaves; V. Curvatures in a flat 
plane. 
Coalescence of Organs, f — Herr K. Beiche points out that true 
coalescence of organs — i. e. the union in the course of growth of organs 
originally distinct — is not a common phenomenon in the vegetable 
kingdom. In the perianth it occurs but rarely. Examples may be 
cited in the calyx-teeth of Fuchsia, and in the petals of Tup a salicifolia 
(Lobeliaceae), of Selliera radicans (Goodeniaceae), and of Carica papaya. 
In the stamens it occurs in Cratsegus oxyacantha, in the staminal tube 
of Tupa salicifolia and other Lobeliace® ; but not, as stated by Eichler, 
in the staminal bundles of Citrus. In the ovary it is a much more 
common occurrence, as in the union of the margins of the carpellary 
leaf in Papilionacete, in the siliqua of Crucifer®, and in the fruit of 
Mirabilis. 
In the vegetative organs true coalescence may take place between 
two different organs either of the same or of different individuals, or 
between a plant and an inorganic substance. In the former case it 
results usually from the destruction of the periderm and the union of 
the two cambial zones, as in the process of grafting. The phenomenon 
is very similar in the case of parasitic plants ; but the degree of 
coalescence between host and parasite varies greatly. In Cuscuta the 
branches of the haustorium perforate the cell-walls of the host with- 
out entering into close combinations with them ; while in Loranthus 
the union is much closer. Instances of close union between a growing 
organ and an inorganic substance are furnished by the union of the 
attachment discs of Ampelopsis and Cissus to a wall, and of those of 
Durvillca to mussel-shells. 
Histology of Fastigiation.f — Herr W. Figdor has subjected the 
phenomena of fastigiation, and of coalescence of growth in general, to 
* Jahrb. f. Wiss. Bot. (Pringslieim), xxiii. (1891) pp. 13-20G (10 pis.). 
t Flora, xlix. (1891) pp. 435-44 (1 pi.). 
I S.B. k. Akad. Wiss. Wien, April 9, 1891. See Bot. Centralbl., xlvi. (1891) 
p. 319. 
