490 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
and minor, and Nerium Oleander), a broad annular zone of tissue is 
separated from tlie apical meristem immediately beneath the growing 
point, which furnishes an initial tissue for the primary vessels, the 
primary phloem groups, aud the fibre-cells, and brings about a sharp 
separation between the pith and cortex. Intraxylary phloem was found 
in all the species, with scarcely an exception. Sclerenchymatous 
cells are a very common phenomenon in the pith. At the base of the 
leaves there are often very interesting emergences, as in the case of the 
oleander. The laticiferous vessels were wanting in only a single species 
(Arduinia bispinosa). The climbing species of the order may be arranged 
under three types, differing in the structure of the wood, of which illus- 
trations are afiorded by Strophantlms scandens, Echites speciosa, and 
Lyonsia straminea. 
(4) Structure of Org-ans. 
Influence of External Factors on the Formation and Form of 
Organs.* * * § — Dr. F. Noll shows that external influences determine not 
only the direction of some organs, but also the position in which they are 
formed ; as, for example, the development of gemmae on Marchantia, of 
aerial roots on climbing plants, &c. In other and more numerous cases 
the formation of fresh organs appears to be independent of external 
forces, and to be determined only by internal forces in the plant, as, 
for instance, in the dorsi ventral structure of many parts of plants. In 
Bryopsis the reversal of the plant brings about a corresponding internal 
organic transformation. 
Epiphyllous Inflorescences.f — H. C. De Candolle has studied the 
morphology of epiphyllous inflorescences in Helwingia japonica (Ara- 
liaceas), Phyllonoma laticuspis (Saxifragaceae), and in some Chailletiaceae, 
Celastrineae, and Begoniaceae. His conclusion is that, in most cases, the 
normal position of the stipules, and the anatomical structure of the leaf, 
show that the epiphyllous inflorescence is a product of the leaf and not 
an axillary bud carried up by a subsequent growth of the axis. He 
regards the leaf and inflorescence together as constituting a single 
phyllome homologous to an ordinary leaf ; and the occurrence of sterile 
and fertile leaves on the same branch as an example of heterophylly. 
Variations in the Flower.:! — Dr. D. Levi Morenos states that out of 
164 flowers of Gentiana Amarella gathered by him in Venetia, no fewer 
than forty-nine exhibited variations from the normal type, in the number 
and degree of development of the divisions of the calyx, in the relative 
position of the stamens, the relative length of the filaments, and other 
points. 
Formation of Flower-buds of Spring-blossoming Plants.§ — Mr. A. 
F. Foerste has investigated the history of the formation of the flower- 
bud in twenty-eight species of American plants which flower in the early 
spring, and finds that, in all cases, the flower has attained a considerable 
degree of development by the preceding August or September. All the 
* SB. Naturhist. Ver. Preuss. Rheinlande, xlvii. (1890) pp. 109-10. 
t Mem. Soc. Phys. et Hist. Nat. Geneve, 1890, 37 pp. and 2 pis. See CR. Soc. 
Roy. Bot. Belgique, 1891, p. 29. 
% Nuov. Giorn. Bot. Ital., xxiii. (1891) pp. 196-200. 
§ Bull. Torrey Bot. Club, xviii. (1891) pp. 101-6 (1 fig.). 
