820 



When we see, thai a ship can hecome overgrown to such a 

 degree during so short a time/as is shown by the case mentioned 

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

 ported by ship and tlius of being carried to otlier countries, where 

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

 conditions of life^. 



If w^e may now assume that the algae can float far across the 

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

 tiie changes of temperature and salinity which a long pas- 

 sage involves. 



As to the first, 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 

 liardly any injurious influence on the algae. It must not be for- 

 gotten, that the changing of temperature proceeds very slow^ly 

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

 changes within certain limits 2. On the other hand, the algae 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 algae 

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



^ That this supposition is right is confirmed by the fact, that we frequently' 

 meet witli algae, belonging to very remote territories, on harbour moles, just as is 

 the case with the inland flora found in harbours and on wharfs. In > Bulletin de 

 la soc. hot. de Frances vol. 35, 1888, p. 364, Hornet for instance mentions 3 La- 

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

 Mediterranean, but which were otherwise never found there. The Fiiciis inftatiis 

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

 ratiis found in Iceland (J 6ns son, 41; can probabh^ also serve as examples. 



Finalh, Dr. Bornet has kindh' informed me by letter of some interesting 

 discoveries. Chorda fihim has been found at the entrance to the harbour of Nice; 

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

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

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

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

 also of France (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. Hypnea miisciformis has been found in the Channel; its true 

 habitat is more towards the south. 



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

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



