ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
585 
C3) Structure of Tissues. 
Structure of Aquatic Plants.* * * § — Prof. K. Goebel describes the 
adaptations to environment in the structure of many aquatic plants, 
both dowering and dowerless ; such as the formation of large intercel- 
lular spaces, the reduction of the conducting tissue and of the mechanical 
system, the splitting of the leaves, &c. The purpose of the abundant 
formation of mucilage appears to be not so much the storage of water as 
protection against animals. Submerged plants agree with shade-plants 
in the suppression of the palisade-parenchyme. The conduction of air 
is facilitated by the formation of air-conducting tissue, aerenchyme or 
pneumatenchyme, or by the occurrence of air- tubes, as in the tubular 
leaves of Isoetes. 
Formation of Mucilage by Aquatic Plants.f — Herr A. J. Schilling 
dnds the formation of mucilage on the organs still in process of forma- 
tion to be a general phenomenon in all water plants. The organs which 
serve this purpose a^e always morphologically trichomes, but vary 
greatly in their form. The mucilage is formed at the expense of the 
cell-wall by the transformation of its outermost layers ; the masses of 
mucilage collecting between the cuticle and the cell-wall. The balls 
which occur within many mucilage organs, composed of Raciborski’s 
myriophyllin,f are not nearly connected with this process. The mucilage 
serves as a protection for the young organs against immediate contact 
with water ; a subordinate function is performed in the protection against 
animals and algae. 
The very numerous dowering water-plants examined by the author 
are arranged in seven groups, viz. (1) The mucilage organs are hairs 
of very simple structure ( Brasenia peltata , Cabomba aquatica ; (2) An 
abundant mucilage is formed in hair-structures which enter into the 
composition of the bud (Nuphar luteurn , Nymphsea alba, Eruryale ferox , 
Victoria regia ; (3) The lower part of the leaf forms a closed sheath, 
the inner surface of which is thickly covered with mucilage-hairs 
( Banunculusflu'itans , Caltha palustris, Limnanthemum nymphseoides, Meny- 
anthes trifoliata ) ; (4) The mucilage organs are composed of a larger 
or smaller number of cells (Aldrovanda vesiculosa , Utricularia vulgaris , 
Callitriche vernalis, MyriopTiyllum spicatum, Ceratophyllum demersum ) ; 
(5) The leaf forms an ochrea at its base ; the whole surface of the 
young plant is covered with mucilage ( Polygonum amphibium , Eumex 
maritimus ; (6) The mucilage is formed at the margin of sheath-like 
stipules (Pontederiaceae) ; (7) The mucilage-organs are intravaginal 
scales ( Vallisneria spiralis, Hydrocharis morsus-ranse , Elodea canadensis , 
Alisma, Sagittaria , Potamogeton, Zostera). Some cryptogamic plants 
also have mucilage-organs, as Salvinia, Marsilea , Isoetes, &c. 
Resin-canals in Abies pectinata.§ — M. J. Godfrin describes the 
course of the resin-canals in the stem of Abies pectinata. From the axis 
they pass to a bud of cortical origin which forms a kind of cup, at the 
* Pflanzenbiol. Schilder., pt. ii. (1893) pp. 215-386. See Bot. Ztg., li. (1893) 
2 te Abtheil., p. 374. 
t Flora, lxxviii. (1894) pp. 280-360 (17 figs.). % Vide infra , p. 588. 
§ Comptes Rendus, cxviii. (1894) pp. 819-22; Bull. Soc. Bot. France, xli. (1894) 
pp. 127-9. Of. this Journal, 1893, p. 60. 
