SCIENCE-GOSSIP. 



2I 5 



He commences with the regulation summary of 

 what was known of seaweeds by "the ancients" ; 

 the three pages so occupied we will leave for the 

 reader, when he gets the book, and proceed to 

 quote Mr. Murray himself. " The first observation 

 commonly made by the student of seaweeds is of 

 the variation of their colours." . . . " An artificial 

 classification of them according to their colours 

 leads to the striking result that 

 it nearly coincides with the 

 natural classification of them 

 according to their structure 

 and development. Such an 

 artificial classification became 

 firmly established, and has left 

 its mark on the names of the 

 natural primary divisions or 

 sub-classes of Algae, viz., the 

 Rhodophyceae, or red sea- 

 weeds ; the Phaeophyceae, or 

 olive-brown ; the Chlorophy- 

 ceae, or green ; and the Cyano- 

 phyceae, or blue-green. A 

 simple experiment proves that 

 fundamentally they are all 

 green, and that the red colour- 

 ing matter, phycoerythrine, 

 the brown — phycophaeine, the 

 yellowish-brown — phycoxan- 

 thine, and blue — phycocyanine, 

 are each something added to 

 the chlorophyll, or leaf-green, 

 that characterises vegetation 

 in general, and by virtue of 

 which plants form organic 

 substances necessary for their 

 nutrition. These additional 

 colouring matters can be ex- 

 tracted by fresh water, leaving 

 the previously red, olive, etc., 

 plants green, and they differ 

 from the green colour in this 

 respect, since it is insoluble in 

 water." . . . "It has been 

 found that the colours of sea- 

 weeds are more or less indicative 

 of their range in depth in the 

 sea, and allowing for numerous 

 exceptions, that there is a zonal 

 distribution of Algae, according 

 to their colours." . . . The 

 interception of sunlight by 

 seawater brings about a state 

 of total darkness at 700 fathoms, 

 probably less, and though sea- 

 weeds do not penetrate to a 

 depth approaching this limit 

 of light, a further consideration 

 will account for their failure. 

 Not only is the quantity of 

 sunlight reduced by its passage 

 through the water, but its 

 quality is affected, as spectro- 

 scopic investigation has shown. 

 It is precisely those rays that 



are most efficient in the work of assimilation by plants 

 that are first intercepted, and only the blue and 

 green rays travel to greater depths. It may be 

 taken then that the red, brown and yellow colour- 

 ing matters, added to the fundamental green, are 

 adaptations to the supply of sunlight." ..." As 

 light is a factor that determines the zonal distribution 

 of seaweeds, and thus affects the local habitats, so 



HlMANTHALIA LOREA. 



Showing button-shaped thallus, and long 

 ichotomous fertile receptacle. — From 



Murray's " Introduction to Seaweeds." 



temperature is the leading influence, among others 

 of minor potency, that affects their geographical 

 distribution." In connection with the subject of 

 light and temperature, Mr. Murray reminds us 

 that the contour of the earth's surface, which 

 brings about the existence of alpine floras for 

 example, has no corresponding influence on the 

 marine flora, since the conditions of illumination 

 check range in depth. 



With regard to the artificial 

 culture of seaweeds in aquaria, 

 it has been found that forms 

 from deep water are peculiarly 

 susceptible to rise of tempera- 

 ture and light. So much so is 

 this the case that their success- 

 ful recovery and transport 

 requires a cloudy day, and in 

 summer the use of ice outside 

 the carriers ; a cool, darkened 

 chamber must be selected for 

 keeping the aquaria. One of 

 the best ways of growing sea- 

 weed is by suspending them 

 in baskets in the sea at proper 

 depths from anchored buoys. 



Mr. Murray next considers 

 the distribution of seaweeds by 

 ocean currents and artificially 

 by their becoming attached to 

 vessels. Naturally the ocean 

 forms far less effectual barrier 

 to the dispersal of land plants 

 than continental areas do to 

 seaweeds, which have no means 

 of bridging them. Among other 

 barriers in the ocean are areas 

 of different temperature which 

 effectually stop some species 

 from invading new regions. 

 "It would be difficult," says 

 the author, "to select three 

 instances of less geographical 

 relationship than the Arctic 

 Sea, the West Indies and 

 Australia. The first has 259 

 species in 1 1 1 genera, the second 

 788 species in 150 genera, and 

 the third has 1,132 species in 

 255 genera. The Arctic Sea 

 has 42 genera and 30 species 

 common with the West Indies, 

 and the same number of genera 

 and 21 species in common with 

 Australia, while out of the two 

 larger totals from the West 

 Indies and Australia there are 

 109 genera and 135 species in 

 common." 



About six pages are devoted 

 to the collecting and preserva- 

 tion of seaweeds, being illus- 

 trated with a picture of Reinke's 

 Dredge. For these pages alone 

 the book is invaluable to the 

 beginner. Their perusal will save him time, 

 expense and loss of temper. Nothing contributes 

 so much to the success of an undertaking as a good 

 beginning. Here are instructions which are simple 

 but effective and unburthened with the elaborate 

 detail which is too often confusing rather than of 

 assistance at the commencement of a study. 



We have now in "Murray's Introduction" a 



