1905-1906.] Formation and Flora of a SJiingle Island. 313 



It will be seen that we have left the presence of two 

 species unaccounted for — Lathyrus pratensis and Achillea 

 Millefolium ; they were growing in the fields, but not pro- 

 fusely, and were not present in the riparian strip. 



Turning now to the second lialf of our list, we may tabulate 

 the results in a somewhat similar way : — 



We find, then, that soil is clearly an important factor in 

 32 cases, moisture in 15, adaptability of the plant in 23, 

 and the possession of a creeping root in 20. Owing to the 

 obscureness of the factors and my own ignorance of plant 

 physiology and cecology, these results are obviously less 

 trustworthy than our first set ; but we give them for what 

 they are worth. The figures given in " total weight of 

 factors " — that is, 5 8 for special suitability of environment, 

 as against 50 for special qualities of fitness in the plants 

 themselves — seein reasonable enough. 



Whether the possession of a creeping root is really as great 

 an advantage as we have here supposed, we do not know. It 

 certainly enables a plant to spread quickly ; and supposing a 

 certain set of plants to arrive simultaneously on untenanted 

 ground, those with a creeping root would probably extend 

 more rapidly than the rest, and so get a first hold over a 

 larger area. We are under the impression, from our own 

 observations, that some creeping plants, such as Kanunculus 

 repens, go on extending throughout the winter ; and if this is 

 the case, the value of the habit is enhanced. We have not, 

 however, been able to get information on this point. 



