Laminaria digitata and Laminaria saccharina. 183 
The Reproductive Process. 
In both Laminaria digitata and Laminaria saccharina the processes 
of reproduction appear to be very similar. The reproductive areas (PI. XIV, 
Fig. 1) consist of modifications of the limiting layer of cells, which 
become elongated and develop into gametangia and paraphyses. 
The gametangia (Fig. d) are about -05 mm. in length, somewhat 
ovoid in shape, and broader at the distal extremity than at the proximal 
end. Under low powers of magnification they appear full of a yellow 
granular substance with the exception of the region nearest their attach¬ 
ment to the cortical cells, where they show a clear colourless layer. 
The paraphyses (Fig. 3) are somewhat flask-shaped, the neck forming 
the attachment to the underlying cortical cells : they average 065 mm. to 
•07 mm. in length, and enclose a narrow cavity in which twelve to sixteen 
chromoplasts are usually present. In number the paraphyses greatly 
exceed the gametangia, but the numerical ratio between them varies widely 
in different specimens. 
By examining scrapings of the reproductive areas, various stages 
in the development of the gametangia can be observed. At first they 
appear to contain a yellowish granular material, interspersed with a number 
of small highly refractive globules, which are soluble in alkalies, but 
insoluble in alcohol or ether. Later, the granular material appears to 
become aggregated into a number of small round bodies of yellowish 
colour, about -0035 mm. in diameter, which slowly increase in size until at 
maturity their diameter is *003 mm. (Fig. d). 
From a consideration of the after life-history of the plants, which 
is described later in this paper, I have come to the conclusion that these 
bodies are the gametes. 
During this process of maturation of the gametes, the small highly 
refractive bodies, present in the immature gametangia, tend to run together, 
and form large well-defined spheres. 
In scrapings containing mature gametangia, many were seen to have 
ruptured at the unattached end with consequent liberation of the contents. 
The actual process of rupture was seen in several cases after keeping 
uninjured gametangia under observation for considerable periods (Fig. 4). 
In sections stained with methylene blue and decolorized with acid alcohol, 
it was found that only the distal extremities of the gametangia retained the 
stain, and the portion stained was larger in mature than undeveloped speci¬ 
mens ; it would thus seem probable that some degenerative change occurs 
in the cell-wall before rupture, and that only this degenerated area retains 
the stain. 
The next stages in development were followed by examination of 
the cultures. 
