820 



When we see, that a ship can become overgrown to such a 

 degree d uring so short a time, as is shown by the case mentioned 

 in the foot-note, the algæ must often have a chance of being trans- 

 ported by ship and thus of being carried to other countries, where 

 they can fix themselves, but of course only where there are suitable 

 conditions of Hfe^ 



If we may now assume that the algæ can float far across the 

 seas, another question presents itself, viz. if they can also stand 

 the changes of temperature and salinity which a long pas- 

 sage involves. 



As to the hrst, it may at once be said, that the changes of 

 temperature and salinity in the seas we speak of are relatively 

 small, and we may therefore also suppose that as a rule they have 

 hardly any injurious influence on the algæ. It must not be for- 

 gotten, that the changing of temperature proceeds very slowly 

 during the passage, and that the algæ are very well fitted to these 

 changes within certain limits 2. On the other band, the algæ are 

 usually very sensible to sudden changes of temperature and sali- 

 nity, as previously mentioned by me, still by no means so very 

 sensible as was formerly assumed. In a paper (Notizen iiber die 

 Cultur und Lebensbedingungen der Meeresalgen, Flora 1895) Olt- 

 manns has already pointed out that freshly gathered marine algæ 

 were much better fitted to resist changes of salinity, than algæ which 



1 That tilis supposition is right is confirmed by the faet, that we frequently 

 meet with algæ, belonging to very remote territories, on harbour moles, just as is 

 the ease with the inland tlora found in harbours and on wharfs. In »Bulletin de 

 la soc. hot. de F'rance« vol. 35, 1888, p. 364, Bornet for instance mentions 3 La- 

 minariaceæ which have been met with a few times in and near harbours of the 

 Mediterranean, but which were otherwise never found there. The Fiicus infkttiis 

 which I found on Lerwick mole (8) and the two isolated habitats of Fnciis ser- 

 raliis found in Iceland (J éns son, 41) can probabh' also serve as examples. 



F'inally, Dr. Bornet has klndly informed me b}' letter of some interesting 

 discoveries. Clwrda filiim has been found at the entrance to the harbour of Nice; 

 the species was never observed at other piaces in the Mediterranean. Helminlho- 

 cladia pnrpiirea was found at the harbour of La Nouvelle, likewise in no other 

 place in the Mediterranean. Bonnemuisonia hamifera which is distributed on the 

 coasts of Japan and California has been found on the coasts of England and later 

 also of F'rance (Cherbourg). The plant is dioecious, and only the female plant has 

 been imported; it propagates by aid of buds which are found at the top of the 

 branches like hooks. Hypnca miisciformis has been found in the Channel; its true 

 habitat is more towards the south. 



' Cp. for instance: Porter, H. C, Abhångigkeit der Breitling- und Unter- 

 warnow-Flora vom Wechsel des Salzgehaltes. (Arch. Ver. Nat. Meckl., 1894). 



