Laminaria digitata and Laminaria saccharina . 181 
The methylene blue is apparently only retained by portions of the cells 
whose walls have partially degenerated. Safranin acts as a body stain 
with an especial attraction for the mucilaginous contents of the cells. 
The structure of the gametangia and paraphyses can best be deter¬ 
mined by making scrapings of the mature reproductive areas with a sharp 
scalpel ; the scraping is teased out on a slide in sea-water slightly tinged 
with methylene blue, and can then be conveniently examined under a 
Y2 inch objective. By this method, after a little practice, it is possible 
to obtain both the gametangia and paraphyses unharmed and completely 
separated from neighbouring cells. 
Cidture methods. 
Small pieces of the mature reproductive areas were cut from plants 
that appeared clean, and free from growths of other Algae. These pieces 
were washed for some time in a stream of sea-water, and gently brushed 
over with a soft brush ; they were then washed in several changes of sea¬ 
water that had been heated to 70° C. and allowed to cool. The object 
of this treatment was to remove as far as possible the growth of diatoms, 
Algae, &c. which is always found infecting the thallus. 
The culture medium used in these experiments was recommended 
to me by Mr. Nelson, who kindly kept me supplied with prepared water, 
and gave me these directions :— 
‘ The following solutions, which are slight modifications of those recom¬ 
mended by Dr. P. Miquel for the culture of Algae, are prepared. 
Solution A. NaN 0 3 
KN 0 3 
nh 4 no 3 . 
Distilled water 
Solution B. Na 2 HP 0 4 . 
CaCl 2 . 
FeCl 3 cryst. puriss. 
HC1 concentrated 
Distilled water 
2 gms. 
2 
1 
100 
33 
33 
4 gms. 
4 „ 
2 „ 
2 3, 
£ When making up solution B, dissolve the sodium phosphate in 40 c.c. 
of the water, and then add first the hydrochloric acid, and then the ferric 
chloride dissolved in 20 c.c., and lastly the calcium chloride dissolved in 
20 c.c. Shake well and filter. 
‘ To each litre of sea-water (obtained from well beyond the Plymouth 
breakwater) 2 c.c. of solution A and 1 c.c. of solution B are added. The 
water is then sterilized by slowly heating it in a flask to 70° C. When cold 
the clear liquid is decanted off from the precipitate which will have formed 
on the addition of solution B, and is stored in sterilized bottles.’ 
