LIGHT IN RELATION TO TREE GROWTH. I93 



did not suffer, and none of them were uprooted by the wind. 

 On the areas inside the ditches a rich flora sprang up during the 

 first summer. Entirely unexpected, there appeared bellflower 

 {Campanula), wild strawberry (/v-a^rt-r/a), hawkweed {Hieracium), 

 sorrel {Run/ex), ironweed or speedwell ( Veronica), willow herb 

 {Epi/obiu»t),sta.x thistle {Cefitaurea), geranium {Gera/num), violet 

 { Viola), five finger {Potentilla), and other herbaceous plants, and 

 in addition there sprang up a number of seedlings of birch and 

 mountain ash. Most interesting and significant of all, however, 

 is the fact that none of these species appeared in the neighbour- 

 ing stand. The herbaceous vegetation which was present on 

 the ground before the experiment, such as sweet vernal grass 

 {Anthoxanthmn), hair grass {Aira), bentgrass {A!:;rosfis), and 

 woodrush {Luzu/a), and which had led a very precarious 

 existence, developed luxuriantly, so that the areas surrounded 

 by the ditches bore green, succulent vegetation, in striking 

 contrast lo the greyish-brown ground cover of the rest of the stand. 



In another pine stand, loo years old, growing on poor soil, 

 several natural openings on which there were no old trees or 

 young growth of any kind were surrounded by ditches and sown 

 with seeds of Scots pine, spruce, beech, and red oak without any 

 preparation of the ground. Similar sowings were made on 

 similar natural openings not surrounded by ditches. On the 

 area inside the ditches there are now remarkably well-developed 

 seedlings of pine and oak, although with characteristics peculiar 

 to shaded plants, and also seedlings of beech and spruce. At a 

 distance of some 7 to 10 feet outside of the ditches, although a 

 part of the seeds did come up, the seedlings of pine, beech and 

 spruce were poorly developed from the start and soon died : the 

 seedlings of oak which still persist have scarcely reached i 5 the 

 height attained by those inside the ditches and will hardly live 

 very long.. In this stand also there appeared in the openings 

 surrounded by the ditches a luxuriant herbaceous vegetation 

 strikingly different from that in the surrounding forest. 



In order to prove also that deficient soil moisture brought 

 about by the competition of the roots was the sole cause of the 

 death of pine reproduction under the shelter of mother trees, 

 Fricke determined the soil moisture in sample plots of which 

 some were penetrated by living roots, while in others the 

 competition of the living roots was eliminated. In all these 

 experiments the proportion of moisture in the soil was invariably 



