368 TRANSACTIONS, NATURAL HISTORY SOCIETY OF GLASGOW. 



even to the utilitarian they are far from being 

 despicable. The cryptogamic botanist finds in their 

 tissues exquisite beauty ; but, at the same time, 

 great perplexity and difficulty in the determination 

 of their variable forms, and this notwithstanding 

 their clearly defined structure. It would be very 

 difficult to state the causes of the variability in the 

 species of Sphagna. The nature of the soil does not 

 seem to have any influence on them, because the 

 granite and greywacke of this district — rocks other- 

 wise uni3roductive in mosses — bear Sphagna in 

 quantity and variety. Moisture and drought, 

 however, must sensibly affect the size, growth, 

 and density of these water-loving mosses. Their 

 beautiful tints of colouring must be the result of 

 vital action, because the various tints they assume 

 are dependent on the colours of the chlorophyllose 

 cells of the leaves. We find the j)revailing tints to 

 be red, rosy-red, ]Durj)le, shades of white, and various 

 shades of green — some varieties receiving their name 

 from their prevailing tint. Perhaps all these mosses 

 have a tendency to vary either into a compact or a 

 squarrose form, of which the two varieties of aS. 

 rigidum — comiJactum and squavrosuluni — afford a 

 very good example. The protean species S. acuti- 

 folium has the greatest number of varieties and 

 forms, and many of these run so imperceptibly into 

 each other that it is almost impossible to determine 

 the exact variety. The only satisfactory method of 

 determination is by a microscopic study of their 

 tissues, because so many species very closely 

 resemble each other in outward form. Nature has 

 no fixed limits in her classification. 



