THE VEGETATION OF SMALL ISLETS. 



BY E. D. MARQUAND, A.L.S. 



If we clear a piece of land, dig the soil and turn it over, a 

 multitude of seedling plants immediately spring up and cover 

 the ground ; and then commences a struggle for existence. 

 Those individuals which are more vigorous than the others, 

 or in some way better fitted for their surroundings, thrive and 

 develop rapidly ; the remainder are crowded out and perish. 

 When the area in which this contest takes place is limited, 

 and has already become fairly well stocked with \egetation, 

 new forms wedge themselves into the crowd at the expense of 

 the older and less vigorous ones. In this case the competition 

 is severe, the intruder has quite enough to do to maintain its 

 own ground, and is hardly able to increase in numbers to any 

 large extent. 



The majority of wild flowers produce an abundance of 

 seed ; and myriads of seeds of all kinds are blown about and 

 scattered far and wide over the face of the country year after 

 year. Yet it is strange that the average quantity of any 

 particular kind of flowering plant appears to remain pretty 

 constant in a locality. Certain species predominate by reason 

 of the profuse abundance of individuals ; they form, so to 

 speak, the groundwork of the vegetation, and determine its 

 general character as a whole. Other species, although ex- 

 tremely common in the same locality, are always much less 

 numerous when you count the specimens. Take for example 

 two plants which may be described as abundant — the Daisy 

 and the Ragwort. They grow in the same kind of situations, 

 they belong to the same natural order, and they each produce 

 a large quantity of seed. Yet the daisy plants immensely 

 outnumber the ragwort plants, probably in the proportion of 

 quite a hundred to one. It is clear therefore that some 

 influence must be at work to check the multiplication of the 

 ragwort while it favours the increase of the daisy, because the 

 relative number of specimens of each kind growing in a given 

 locality does not perceptibly vary, even in the course of many 

 years. " If we ask ourselves," says Darwin, in his Origin of 

 [1909.] 



