Development of Laminaria bulbosa , L amour . 47 
consequence of energetic cell-formation. This bulb increases 
rapidly in diameter and grows downwards, pressing closely on 
the substratum. It thus surrounds the root-threads which 
spring from the middle of its lowest part, and causes their 
destruction. At this stage of development the sole means by 
which the plant is fixed is the basal bulb. It may be that the 
root-organ of Z. solidungula has remained stationary at this 
stage of development. In our common species there are 
developed from the upper part of the bulb and neighbouring 
parts of the stalk several successive whorls of root-branches. 
The median strand of elongated cells which is found in the 
stalk is wanting in these organs. The root-branches grow 
towards the substratum and become applied to it with great 
force : so much so, that in older specimens the original fixing 
bulb is loosened from its attachment and lifted away. This is 
certainly the case with L. hyperborea which possesses a stronger 
and more regularly developed organ of fixation than the other 
species. Alaria has a similar organ, but frequently less 
strongly developed 1 / As no special mention of L. bulbosa is 
contained in the passage just quoted, I presume that Stromfelt 
has not met with it in the earlier stages, for such a deviation 
from type would not be omitted even in a prefatory notice. 
After a very moderate development of processes from the 
basal part of the stalk, further outgrowths from this part of the 
plant appear to cease. All further development of fixing 
organs is now confined to the ridge of tissue already referred 
to. The portion of the stalk below the ridge does, however, 
for a certain time grow in length and thickness, and continues 
to be the longest part of the stalk. 
The development of the ridge, and its gradual transfor- 
mation into a bell-shaped organ, are represented in the series of 
figures accompanying this paper. These figures may be briefly 
interpreted by referring to Agardh’s short description already 
quoted. In Fig. 2 the stalk is already assuming its flattened 
form. This is emphasized in Fig. 3, where also the ridge is 
Bot. Centralblatt, xxxiii. p. 398. 
