610 
great quantities of loose Algæ are especially carried along the bottom by westerly 
storms, when the currents run from the northern areas with comparatively high 
salinity to the Belt Sea and the Baltic where the salinity of the water is lower, 
and they may then come to rest in localities where the water is less agitated and 
the external conditions altogether rather tranquil. In such localities the loose Algæ 
may find a tolerably permanent place of residence, whether they lie loose on the 
bottom or they are retained between the rhizomes of Zostera-plants or between 
attached Algæ. Loose forms of several species of Algæ are often found entangled 
with each other in such places. The power of keeping alive for a long time in a 
loose condition depends not only on the consistency of the frond but also on its 
ability to support the different external conditions in the new place (salinity, 
variation of temperature etc.), and on its power of increasing and branching 
after having been detached from the substratum. As will be seen in the following, 
the species here in question show great differences in their power of adaptation to 
the loose condition. 
Phyllophora membranifolia does not seem very willing to vegetate in a loose condi- 
tion. Detached fronds may be met with, but they are not different from the attached 
ones and seem unable to grow after having been detached. (Comp. p. 521). 
Three loose forms of Chondrus crispus were mentioned above (pp. 506—507); 
they occur rather rarely and in small quantities, and it is doubtful whether they are 
able to vegetate and propagate in the loose condition. Specimens of f. incurvata 
showing a callus disc at the lower end of the frond cannot have lived long after 
the disengagement for the callus must be supposed to have been produced on the 
wound surface where the frond has been loosened, and the aberrant shape of the 
frond must, therefore, be supposed to have been accomplished by transformation of 
the frond, not by innovation. 
Rhodymenia palmata occurs in a loose condition in the Baltic north of the 
Isle of Moen (Bm), where the species cannot live in the normal, attached state, 
owing to the low salinity of the water. These specimens have undoubtedly been 
carried into the Baltic from Øresund when the bottom current through Øresund 
overflows the threshold at Saltholm; they resemble those growing attached in Øre- 
sund. They undoubtedly keep alive for some time, but it is doubtful whether they 
can propagate for any long period. At any rate, as the species can continually be 
introduced in this part of the Baltic, it is understandable that it has often been 
met with in this area, like many other loose Alge. The great length of the fronds 
gives evidence of a continued growth in the loose state. 
Phyllophora Brodiwi which is very common in all the Danish waters often 
occurs in a loose condition of various shapes. The most common form is f. conca- 
tenata which is most frequently met with in the Zostera region; it is characterized 
by long fronds alternately filiform and flat, lanceolate, branched by dichotomy and 
by proliferations. Nearly related to it is f. filiformis, the frond of which is very 
narrow, almost entirely cylindrical. F. stellata has a quite different shape, the dichotom- 
