79 373 



leads us to the following result: 34,5 "/o of these species are found growing in loose mouldy 

 soil, in woods, hedgerows etc.; 30,09 on wet soil (banks of ponds and lakes, wet meadows, 

 mud); five other types of habitat have together only 35,30 "lo (see p. 364). Even though the 

 subjective estimate may make itself felt to a certain degree in determining the character of 

 the habitat in each case, and all Danish species are not included, the superiority of the two 

 first-named types seems sufficiently pronounced to warrant our asserting with confidence that 

 loose, moist or wet or watery soil furthers the formation of underground runners. That 

 root formation is furthered by moisture of air and soil is a well known fact. 



Origin of u n derground runners. I consider that underground runners are descended 

 from aerial shoots, and could imagine that the iirst step was taken by some orthotropic 

 aerial shoots, somewhat prostrate at their base, which from being at first merely prostrate, 

 without secondary rootlets, afterwards took root, such shoots being later again transformed 

 into stolons, and these finally becoming underground runners, as deposits of earth or waste 

 products of the forest growths, covered them up. As the light became excluded, thej' would 

 lose colour, develope scale leaves, etc. In support of this hyi)othesis, I may adduce the 

 many instances of one and the same species being both sloloniferous and suboliferous isee 

 p. 365) and the fact that the one ty])e of runner often may easily be led over into the other (Stahl, 

 GoEBEL). It may further be noted that some underground runners still have hairs (fig. 19, 

 Mercnrialis; species of Mentha, Achillea millefolium, Stachijs palustris. Sa.rifiaya riinilaris; see 

 p. 365); others have still stomata (Tijpha, according to Olivier). That some species are 

 constant in their present form is seen from Adoxa moschcllatina, the rhizome of which forms 

 scale leaves even when exposed to light. This question, the constancy of characters, also 

 arises with regard to tubers in species of the potato type. 



