276 REPORT OF COMMISSIONER OF FISH AND FISHERIES. 



covering of rocks and stones between high and low water marks on 

 the coast from Nova Scotia to New York. There are two prominent 

 species of tliese, the round-stalked and the flat-stalked. Tlie priiicii>al 

 species of kelp, viz, the ribbon-weed and the broad ribbon-weed or 

 devil's apron, are common on the rocks at and below the low- water 

 mark from Newfoundland to the New Jersey coast. In the north of 

 Europe both of these species are used for food to a considerable 

 extent. Dulse, Irish moss, and other species may also be used for 

 fertilizer, but the quantity obtained is so small that they are of little 

 importance in this connection. 



The principal fertilizing agencies in aquatic plants are nitrogen and 

 potash ; the quantity of phosphoric acid is very small, amounting to 

 only about 10 per cent as much as the above two combined. Seaweeds 

 also contain considerable quantities of lime and magnesia. By the 

 addition of some material containing a large percentage of phosphoric 

 acid, as bone meal, for instance, a "complete fertilizer" is formed. 

 This is frequently very important in order to secure the full value 

 of the nitrogen and potash contained in the seaweeds. 



According to analyses made by the Rhode Island Agricultural 

 Experiment Station," the average percentage of fertilizing constit- 

 uents and of water contained in various aquatic plants in the fresh 

 state collected at different seasons on the coast of Rhode Island is as 

 follows. For convenience of comparison , analysis of average barnyard 

 manure is ajipended. 



Materials. 



Nitrogen. Pl^°/?^°"« 



acid. 



Potash. 



Water. 



Rorkwppd, flat-stalkod 



Rockwei'cl. ri mud-stalked 



Broad riblion-woed, or devil's apron 



Ribbon-weed, kelp, or tangle 



Dulse --- 



Irish moss 



Eelgrass 



Barnyard manure 



Per cent. 

 .38 

 .24 

 .23 

 .17 

 .37 

 .57 

 .35 

 .49 



Per cent. 

 .12 



.OH 



.m 



.05 

 .09 

 .13 

 .07 

 .32 



Per cent. 



.65 



.64 



.31 



.16 

 1.07 

 1.03 



.32 



.43 



Per cent. 

 76.55 

 77.26 

 87.50 

 87.99 

 86.25 

 76.03 

 81.19 



The total quantity of the fertilizing ingredients in plants is very 

 small in proportion to the weight of the material, this being due prin- 

 cipally to the large content of water. Usually at least 75 per cent of 

 the weight of aquatic plants consists of water, and about 80 per cent 

 of the remainder is a soft, easily decomposable form of organic matter. 

 The plants decompose rapidly, and the water separates from them 

 quickly, the weeds left in heaps on the beach being reduced to one- 

 half or one-third of their original bulk in a few weeks. Since mncli 

 of the fertilizing constituents, especially the nitrogen, wastes away in 

 this process, it is important that the plants be used within as short a 

 time as practicable after tliey have been collected. For the same 

 reason it is mucli better to collect weeds directly from tlie rocks, or 



" Bulletin No. 21 of Rhode Island Agricultural Expei-iment Station, January, 1893. 



