712 
Yendo.—The Development of 
In a primary stipe which is a few millimetres in length, the medulla is quite 
wanting. As the meristematic point lies in the transitional region, and as 
the hyphal cells are generated after the precortical layers have been formed, 
the lack of the medullary tissue in the primary stipe is to be expected. 
Barber, 1 speaking of the stipe of Saccorhiza bulbosa , states that in the 
portion below the ridge and in the hapteres there is no formation of the 
hyphal tissue. Setchell 2 noticed also in a young frond of 5 . dermatodea 
the presence of the hyphal cells at the transitional point only. 
The primary root of a plant measuring about 2 cm. in total length is 
round and disc-shaped with a diameter of about i mm. (Fig. 40, PL LV). 
The periphery is still felty at this stage. When a frond has attained the 
height of 7 cm. or so, the disc-shaped root extends horizontally, forming a 
haptere or scutellum with an uneven surface and a few shallow notches on 
the margin (Fig. 41). The periphery is now thick and rounded, and is 
undoubtedly constructed of a compact tissue of minute cells. Indications 
of the future rhizines may be seen as insignificant outgrowths around the 
point just above the primary haptere. These rhizines quickly elongate, the 
primary haptere extending as well, first horizontally, but soon bending down¬ 
wards to form the primary holdfast (Fig. 42). The further development 
consists in the addition of new whorls of rhizines above the older ones, the 
diameter of the stipe and rhizines increasing at the same time. 
The part of the primary stem in which the medulla was absent is 
practically lowered down as the stipe elongates, and becomes buried within 
a part of the axis of the holdfast. And this part decays away before long 
with the primary haptere. Hence, in an adult form, no part of the stipe is 
devoid of medulla. 
The two species of Laminaria above mentioned are characterized by 
the constant presence of lacunae in the stipe as well as in the lamina. In 
these, the lacunae are situated close along the periphery and are regularly 
arranged, with narrow intervals between one another. 
A search for the lacunae in young specimens gave a negative result. 
In a specimen with the total height 54 mm., maximum breadth of blade 
21 mm., and diameter of stipe 2 mm., no indication of the lacunae could be 
seen in the whole length of the plant. The younger specimens of course 
were devoid of them. These searches have been carried out by making 
sections at every millimetre of the frond, and also by staining, in to to, in 
aqueous solution of aniline blue. The blade of Laminaria , suitably fixed 
beforehand, and preserved in alcohol, is dipped in aniline blue (after Ranvier) 
for half an hour; then washed thoroughly in 70 % alcohol. The lacunae 
only are then stained a deep blue. Thus the presence and the distribution 
of the lacunae may be satisfactorily demonstrated. 
The specimens collected in July and August, which had the stipes 
1 Barber : 1 . c., p. 54. 2 Setchell: 1 . c., p. 197. 
