628 
Hunter .— The Aerating System of Vicia Faba. 
Seeds of Vicia Faba were soaked in water for twelve hours and then 
sectioned. The structure of the testa is similar to that of Phaseotus as 
described by Haberlandt, 1 and to that of Pisum sativum as described 
by Detmer. 2 The general arrangement of the tissues of the seed-coat is as 
follows: 
(a) An epidermis composed of thick-walled cells of palisade pattern. 
This layer is compact, and intercellular spaces are completely absent. 
(b) A layer of pillar-shaped cells alternating with large intercellular 
spaces. This form of cells is probably determined, as in water plants, by 
a demand for increased air space, without interfering with the movement 
of water from without the seed to those portions which are in need of it, 
(c) Tissue consisting of parenchymatous cells having their greatest 
axis in a direction parallel to the surface of the seed. 
Intercellular spaces are present in this tissue, but 
they are of quite a different nature from those of the 
middle layer, and are quite typical of the intercellular 
spaces which usually occur in parenchymatous tissue. 
This layer of cells forms nearly one-half of the 
soaked testa, but in the dry seed the cells are in 
a collapsed condition, and only regain their turgid 
state on the absorption of water. 
Text-fig. i shows the general arrangement of 
these different layers of cells which go to compose 
the testa. 
Thin hand-sections of the cotyledon were washed 
gently in water in order to remove the masses of 
Fig. i. Testa of Vicia reserve material which would have prevented a careful 
Faba , transverse section . . . , 
showing the three types of examination of the tissues. The sections were then 
of SU the middfe^aye^are mounted in glycerine jelly. The cotyledon was 
diagonally shaded, x 180. found to consist of three distinct types of tissues 
(a) An epidermis consisting of small, cubical, 
compact cells. Stomata were completely absent, and the layer possessed 
no intercellular spaces, 
(b) Vascular tissue devoid of intercellular spaces, 
(c) Parenchymatous storage tissue. 
The storage tissue is permeated by an intricate aerating system. This 
does not consist merely of the triangular or rectangular intercellular spaces 
such as are figured by Sachs, 3 in the case of cells from the cotyledon of 
Pisum sativum . The aerating system of the parenchymatous storage cells 
of Vicia Faba forms a conspicuous feature of the sections, and consists 
1 Haberlandt: Sitzungsb. der K. Akad. Wien, Naturwissenschaften, Bd. 75 (1877), p. 33. 
2 Detmer and Moore : Practical Plant Physiology, p. 192. 
3 Sachs : Lectures on the Physiology of Plants, p. 52. 
