MOTION AND GROWTH IN THE FUCACE^. 19 



On the Motion Accompanying Assimilation «wc/ Growth 

 in the Fucack^. By Prof. P. Martin Duncan, M.B., 

 Lond., F.R.S., &c. (With Woodcut.) 



("Read in Section D, at the Meeting of the British Association at Bradford, 



l'873.) 



How do the dark olive- coloured Fucoids res)3ire ? and 

 whence do they ohtain their recondite elementary belongings ? 

 are questions which most physiological botanists have asked 

 themselves during their sea-side rambles. Authority answers 

 readily enough respecting the respiration, and will probably 

 insist that the nitrogenous and non-nitrogenous combinations, 

 the iodine, bromine, the potash, soda, and the phosphates 

 are separated from the sea-water in which they all exist as 

 inorganic substances. It is assumed that the plant exercises 

 a selective function, and that the rushing wave yields up the 

 elements in binary compounds to the superficial cells. These 

 can alone be the agents of the nutrition of the plant, for 

 there is no true root and no special circulatory system. 

 Washed by the sea, the cell-wall permits of an endosmosis, 

 and a liquid enters which is barely salt, and which contains 

 the well-known ultimate principles of these cellular plants. 

 Were the colouring matter of the Fucus green, and were its 

 proximate compounds only combinations of C,H,0, and 

 C,H,0,N, the effect of light and life on the carbonic acid and 

 free ammonia in the sea water would be deemed sufficient to 

 account for the assimilation. 



But the colouring matter is peculiar. The plants may be 

 exposed to the glare of the sun, or hidden in cavities where 

 there is ever a gloomy darkness, with the same result on their 

 pigment. The presence of sufficient ammonia in sea-water to 

 account for the weight of nitrogenous matters in the rapidly 

 growing Fuci is a myth, and it is quite as probable that 

 decaying Fuci contribute the small percentage of salts of 

 iodine and bromine to the sea as that they should enter the 

 plant in solution in pure sea water. 



The Fuci like the shore, and live best where the waves are 

 saturated with air, and doubtless much of the nitrogen may 

 come from this source. Is there not another ? is a question 

 which commends itself, and which may be answered by a 

 second : why should not these plants without green chlo- 

 rophyll 1 absorb organic matter in a state of solution ? matter 



» [Millardet has detected chlorophyll in Fucacea, 'Comptes Rendus,* 

 Feb. 22ad, 1869.— Eds.] 



