Laminaria saccharinu. 
299 
with was the impossibility of removing the Safranin from the walls by any 
of the ordinary methods, but a solution of dilute glycerine followed by 
London blue was found to produce the desired result. The London blue 
not only removes the Safranin from the walls, but also stains the callus, 
as does Water blue. Moreover it has the additional property of staining 
callus in places where Water blue has no effect, presumably because the 
callus is not sufficiently hydrated. 
The acid-violet method 1 both by itself and in conjunction with 
Safranin was found to be useful, and Water blue made up with Aniline was 
occasionally employed alone. 
London blue alone was used in the investigation of callus, and Methy- 
lene blue, Thionin, and Fuchsin were found to be convenient cell- wall 
stains. 
III. Macrocystis pyrifera. 
A. General Anatomy. 
As no young plants of Macrocystis were available, my investigations of 
the development were confined to the study of the apical portion of an 
adult specimen. 
Stage i. In the youngest part of the growing thallus the tissues are 
already differentiated into cortex and medulla, the breadth of the cortex 
being somewhat greater than that of the medulla. 
The outermost layer of the cortex is composed of regularly arranged 
isodiametric cells, which are in a state of active division, and give rise 
to rows of elements, the radial arrangement of which can be traced in 
transverse section throughout the cortex, and often appears to be continued 
into the medulla. About eighteen layers of cells make up the entire cortex, 
the counting being made along any such radial row. The outer eight 
or ten layers are certainly of secondary origin. In longitudinal section 
they are seen to be composed of thin-walled parenchymatous elements, 
sparsely provided with contents, and on the extreme periphery of the 
section mucilage canals with small patches of secretory cells (cf. Will 2 ) 
are present in abundance. 
In longitudinal section this outer cortex is sharply marked off from 
the inner, which is made up of much more elongated cells, whose longitudinal 
walls are considerably swollen, while many of their transverse walls are 
very thin and give the impression of having been quite recently formed. It 
seems certain that this inner cortex represents the primary cortical tissue of 
the thallus, the cells of which have given rise to these characteristic elements 
by means of longitudinal stretching followed by rapidly succeeding cross 
1 Gardiner, 1 . c., 1898, p. 508. 
X 2 
3 Will, 1 . c., 1884. 
