816 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
equilibrium ; (2) when it departs from its position of equilibrium, it 
returns to it by curving at the point where it bends most easily. 
Coalescence of Organs.* — According to Herr W. Figdor, a true 
concrescence of parts originally distinct is always effected by the 
formation of new cells. There are four degrees of union to be dis- 
tinguished, viz.: — (1) A permanent concrescence (tuber of Cyclamen 
europseum, turnip) ; (2) Concrescence with subsequent formation of 
periderm (potato) ; (3) A union depending partly on concrescence, 
partly on the transformation of the injured cells into a cementing 
mucilage (beet, carrot, dahlia, artichoke) ; (4) In some cases under- 
ground tuberous organs, once separated, cannot again enter into organic 
union ( Iris germanica , Begonia, Stachys affine). In order that true con- 
crescence may take place, a definite minimum of transpiration must not 
be exceeded ; there must be a sufficient space between the cut surfaces 
for the development of the new cells ; and a certain pressure which 
apparently acts as an irritant must be applied to the parts that are 
to unite. 
Fruit and Seeds of Compositse.t — Herr R. Loose has compared the 
structure of the pericarp and seed-coat of 228 species of Composite. 
An aerial tissue is usually present, either uniformly distributed on all 
sides, or in special wings or cushions. The pericarp or testa generally 
contains mechanical elements, except in the case of very small seeds 
which are entirely enclosed in the involucre. Contrivances for fixing 
the fruit in the soil are rarely wanting. 
Fruit and Seeds of Cyperacese-J — Herr H. Wilczek describes in 
detail the structure of the seed, integuments, and fruit of this natural 
order, taking as his type-species Car ex paradoxa. 
In the utricle the following distinct tissues can be distinguished : 
— the inner and outer epiderm, the swelling tissue, the aeriferous 
tissue, the vascular or mestome-bundle, and the bast or stereome-bundle. 
In the pericarp three layers may be distinguished, — the outer epiderm, 
the middle or stereid-layer, and the inner epiderm. The epiderm of 
the pericarp differs from that of grasses in having its outer wall not 
thickened, its inner wall strongly thickened, and in the presence of 
sclereids. The seed has in contrast to that of grasses a distinct funicle. 
It has an endosperm, but no perisperm. With regard to the mode of 
germination, the Cyperacese belong to the palm-type, in which the 
absorbing organ, usually small and conical in the dormant seed, enlarges 
greatly on germination, and penetrates deeply into the endosperm. 
The structure of Carex paludosa and of species belonging to some 
other genera is compared with that of C. paradoxa ; and the species of 
Carex are grouped under two types, viz. : — (1) Utricle stout, funda- 
mental tissue differentiated into aeriferous and aquiferous (C. paradoxa, 
paniculata , teretiuscula , &c.) ; (2) Utricle thin ; fundamental tissue not 
differentiated (0. paludosa, stricta , ampullacea, depauperata, &c.) The 
strength of the pericarp is in inverse proportion to that of the utricle. 
* SB. K. K. Akad. Wiss. Wien, c. (1891) pp. 177-200 (2 pis.). Cf. this Journal, 
ante , p. 68. 
f ‘Die Bedeutung d. Frucht- u. Samen-schale d- Compositen,’ Berlin, 1891, 
60 pp. and 2 pis. See Bot. Central bl., 1892, Beih., p. 263. 
X Bot. Centralbl., li. (1892) pp. 129-38, 193-201, 225-33, 257-65 (6 pis.). 
