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the surface of the eartli the stem is bent horizontally at 

 riglit angles). The siibterraneous parts of stems of these 

 piants are negative geotropic as fig. 5 b and c show. I di- 

 stingLiish two types of growth-form: 

 Erect stems (negative geotropic): (erect). 

 Prostrate stems (transversely geotropic): (prostr). 



At the beginning of autumn some of the most erect types 

 bend their stems downwards horizontally, but the apices of 

 the stems are always erect, and thus these phenotypically 

 prostrate piants are easy to distinguish from the other geno- 

 ty pie al ly prostrate. 



18. The colour of the stem: 

 I distinguish 2 types: 



Piants containing a large quantity of anthocyanin 



(atrop = atropurpurea): dark violet stems. 

 Piants with fresh green stems {n.atrop = non atro- 

 purpurea). 



In the dunes of West-Jutland and Læsø nearly all the 

 pansies are atropurpurea. The piants from the fields are 

 usually non atropurpurea. The piants with albinotic flowers 

 have pale green leaves and stems {chlorina), but as this 

 character is coupled with alba, I have not taken it into 

 consideration here. 



19. Duration of Life: 



Viola tricolor and arvensis are as a rule annual. They are 

 Therophytes which regard the dry summer-time as the 

 most unfavourable season. In many fields arvensis only lives 

 from autumn to early summer (is winter-annual). V. tricolor 

 can better survive the dry season. On the other hånd, in 

 dunes and in pine forests most individuals of Viola tri- 

 color are perennial. An essential condition for perennity in 

 our latitudes is that the piants either are able to produce 

 subterraneous side-branches or are able to ramify strongly 

 in the surface of the earth. Commonly Viola tricolor and 

 arvensis lack this capacity in contradistinction to V. cornuta- 

 calcarata. In dunes the sand-heaping and in pine woods 

 the falling of acicular leaves replace this capacity of the 

 plant, as the lower parts of the stems with their buds 

 are covered by these agencies. From the covered parts the 

 piants shoot adventitious roots and subterraneous branches 



