1910.] Composition of Seaweed and Use as Manure. 463 



bays in many districts. It is not a true grass, but is more 

 nearly allied to pond weed (potamogeton). Salicornia is a 

 chenopod; Glyceria is a true grass; both are salt marsh or 

 seaside plants. Sea mat is the tough brown flat structure 

 commonly found with seaweed ; in the sea it was a colony of 

 zoophytes, but when cast up on the shore and dried the 

 organisms perish. The organic matter present contains 

 about 9 per cent, of nitrogen, a high figure characteristic 

 of animal residues, but much in excess of anything found in 

 plants. The small shells and debris contained no less than 

 21*8 per cent, of calcium carbonate. 



An inspection of Table I. shows that the nitrogen in the 

 dry matter ranges from 1*25 to 27 per cent., being lowest 

 in the Croyde samples taken in summer, and highest in the 

 Thanet samples collected in winter. The total ash is usually 

 25 to 35 per cent., 1 to 5 parts of which are silica arising partly 

 from silicates and partly from sand entangled with the weed. 

 Very little phosphoric acid is present, sometimes less than 

 o'i per cent., and never much more than 0*5 per cent.; the 

 potash, on the other hand, varies between 2 and 6 per cent., 

 Laminaria containing more potash than Fucus. Soda is 

 present in about the same amount as potash, and there are 

 smaller quantities of lime and magnesia. 



The composition of seaweed shows some variation with the 

 time of cutting. Mr. Toms' analyses of Jersey seaweeds, made 

 at different times of the year, indicate that weed cut in October 

 is poorer than that cut in March or May. His results are : — - 





Fresh weed. 



Percentage composition of the dry matter. 



Water. 

 77'4 



73 "4 

 76-6 



Dry 

 matter. 



Organic 

 matter. 



Nitro- 

 gen. 



Ash. 



Potash. 



Lime. 



Phos- 

 phoric 

 acid. 



Fucus (cut). 



March 



May 



October 



22*6 



26-6 

 23-4 



81 -4 

 79"5 

 79-3 



I 91 



1-98 

 116 



1 8 -6 

 20 "5 

 207 



2'62 

 2'26 

 2-50 



1 '3 



2'I 



1 '3 



0-36 

 0"20 

 0-85' 



Laminaria 

 (drift). 



March 



May 



October 



87-0 

 78-0 

 82-0 



13-0 

 22 *o 

 18-0 



65-0 

 74-0 

 817 



3-06 



1*94 

 0-96 



35'o 

 25-6 



i9'3 



3 '45 

 3 '93 

 2*34 



1-96 1*29 

 170 170 

 1-65 j 1-65 



1 



(Notes on Farm Chemistry in Jersey, 1905.) 



These analyses further show that Laminaria drifting in from 



