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depend as a rule not only on the thin layer of humus or rich 

 organic soil, but also on the cover of mosses and roots of ferns 

 and the smaller herbaceous plants composing the undergrowth, 

 with which the tree roots are intermingled, for their sustenance, 

 support and the retention of proper moisture conditions. 



In other words, the wet native forest is composed of a society 

 of plants consisting of trees and undergrowth, the upper story of 

 light-demanding trees giving shade to and protecting the lower 

 or second story of shade-enduring plants, this lower story in turn 

 retaining the moisture for and giving food in the form of decom- 

 posed ^•egetable matter to the shallow-rooted systems of the 

 higher trees under which they thrive. Through long association 

 these two main plant forms have accustomed themselves to each 

 other and when one is disturbed the other wall suffer. With the re- 

 moval of the upper story of trees, the sunshine is admitted to the 

 lower story of plants, the ground is dried out, moisture condi- 

 tions are unfavorably affected, and the plants unaccustomed to 

 the new conditions expire. If the lower or second story is re- 

 moved, the absence of the protective cover for the roots of the 

 trees induce changes in soil conditions, the roots dry out for 

 lack of moisture and proper plant food, and the trees are gradu- 

 ally weakened, are exposed to the attack of injurious insects and 

 wood-destroying fungi, and gradually die. Any disturbing 

 element, such as cattle in the forest, wdiich enters and begins to 

 change the ideal conditions for this plant association will upset 

 the balance of nature with disastrous results. When once this 

 happens, the cycle of destruction begins, and if allowed to con- 

 tinue the forest is doomed. Insects and fungi rarely attack 

 healthy, vigorous trees, but are always on the watch for trees 

 which have been weakened by disturbed conditions. 



With light and soil conditions altered and the sunshine ad- 

 mitted to the ground, the way is then paved for the entry of 

 foreign plants. These, as a rule, are faster growing than the 

 indigenous ones and are therefore able to force back the native 

 growth and conquer the ground so completely that the trees are 

 not able to reseed themselves through the thick matted ground 

 cover. Hilo grass and staghorn fern are two of such plants which, 

 following up disturbances in forest conditions, have wrought im- 

 mense damage on lands where, if the heavy dense forest had 

 remained, they would never have obtained an entry on account 

 of the heavy shade. 



Formation of Ohia Forests. 



The establishment of an ohia forest on a new lava flow gives us 

 a clue as to the difficulties of tree growth under our peculiar 

 conditions, and the importance of non-interference with the 

 struggle for existence which the trees of such a forest are forced 

 to maintain in combination with other plant forms. 



The ohia lehua, which is the chief tree in our protection for- 



