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the surface of the earth the stem is bent horizontally at 

 right angles). The subterraneous parts of stems of these 

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

 stinguish 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 plants are easy to distinguish from the other geno- 

 typically prostrate. 



18. The colour of the stem: 

 I distinguish 2 types: 



Plants containing a large quantity of anthocyanin 

 {atrop = atropurpurea) : dark violet stems. 



Plants with fresh green stems (n. atrop = non atro- 

 purpurea). 



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

 pansies are atropurpurea. The plants from the fields are 

 usually non atropurpurea. The plants 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 hand, 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 plants 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. corn ni a- 

 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 huds 

 are covered by these agencies. From the covered parts the 

 plants shoot adventitious roots and subterraneous branches 



