Barley Grain in Relation to Localized Water Absorption . 407 
coverings under these conditions, but hardly any further growth took place. 
Before the rupture of the grain-coverings occurred, the micropylar point and 
the furrow tissue at the germinal end became very deeply stained. Cutting 
round the coverings and lifting the scutellum, the surface opposed to the 
endosperm showed a gradation of colour which was more intense on the 
furrow side. The point of the coleorhiza—formed by the embryonic 
appendage—was deeply stained when it appeared through the coverings. 
Later, the endospermic bag became very turgid, and burst at the germ end 
of the furrow. The non-removal of the products of ferment action, owing: 
to the absence of embryo growth, with a consequent rise of turgor pressure, 
conduced to this result. 
Normally it would appear that after the rupture of the coverings at 
the micropylar end by the development of the coleorhiza, the endospermic 
bag, bounded by that part of the membrane which remains intact and the 
scutellum, forms a distinct unit. At this stage the cuticular membrane of 
the tegmen serves to prevent the loss of the now more or less fluid reserves 
and to protect this rich pabulum from the attacks of fungi and bacteria. 1 
(b) Grains were steeped for varying periods in a 3 per cent, solution 
of silver nitrate and the sections cut from them were exposed to light, 
precautions being taken to guard against the possible diffusion of the solute 
over the sections. With short periods of steeping the silver nitrate showed 
no effective entry, beyond a darkening or an occasional blackening of the 
tissues of the furrow and the cells of the embryonic appendage. After 
longer periods of steeping the embryo and the proximal end of the endo¬ 
sperm were dark brown, whilst towards the apex of the grain infiltration 
along the sheaf-like mass of cell-walls and gradual spreading across the 
section was shown. 
The whole series of experiments described in this section represent an 
endeavour to locate the path of entry of solutes into the grain. From the 
results obtained, the following general conclusions were drawn: 
(a) That, as with water, solutes gained entry at the micropyle. 
(b) That in, the earlier stages of immersion of grains in aqueous 
solutions, the balance between the solute and water was determined solely 
by the selective action of a tract constituting a specialized local path 
of entry. 
1 In this connexion my attention has been called recently to the work of J. Beauverie, ‘ Les 
Germes de Rouilles dans les Semences de Graminees Rev. Gen. de Bot., 25 bis, 1914, from which 
is taken the following extract: ‘ Dans tous les cas de grains de Graminees contamines par le 
mycelium de rouille nous avons pu constater que le dit mycelium ne penetre jamais ni dans 
1’albumen, ni dans Pembryon. II parait arrete dans sa progression vers ces organes par la couche 
membraneuse fortement cutinisee et sclerifiee, d’origines diverses, qui recouvre la couche a aleurone 
dans le cas des fruits nus et par les epidermes contigus de la glumelle et du pericarpe dans le cas des 
fruits vetus. Ce n’est que lorsque cetle zone membraneuse vient a etre rompue par une cause acciden- 
telle, un traumatisme ou peut-etre 1’action de certaines bacteries, que les bacteries et les mycelium 
peuvent pen&rer.* 
