MINEKAL MATTEES IN FALLEN LEAVES. 33 



The loss of inorganic food-constituents, which the 

 foliaceous trees suffer by the fall of the leaves, is trifling. 

 When the leaves have attained their full formation, the 

 cells of the bark receive a copious supply of amylum, 

 which substance completely disappears from the cells 

 in the boss of the leaf-stalk (H. Mohl). Even long be- 

 fore the fall of the leaves, their sap is considerably 

 diminished, while the bark of the branches is, just 

 at that time, often actually overflowing with sap 

 (H. MOHL). In accordance with this fact, the analysis 

 of the ash of the leaves shows that the amount of alkali 

 and phosphoric acid in them decreases immediately 

 before the fall ; the fallen leaves contain such trifling 

 quantities of these constituents, in comparison to their 

 mass, that it is difficult to account for the injurious 

 consequences arising from the raking up and removal 

 of the fallen leaves in woods. (See Appendix A.) 



A similar reflux of the assimilative products appears 

 to take place in the grasses ; when from the intense 

 heat of summer the leaves begin to decay, chemical 

 analysis reveals in the yellow leaves scarcely any traces 

 of nitrogen, phosphates, and alkalis ; and, indeed, ani- 

 mals instinctively turn from all kinds of fallen leaves, 

 and refuse to feed on them. 



In annuals and biennials the organic action results 

 in the production of fruit and seed, after which the 

 activity of the root comes to an end ; in perennials, the 

 production of seed is rather an accidental condition of 

 their permanent existence. 



The biennial can bestow more time than the annual 

 in gathering the material necessary for the production 

 of seed and fruit, which closes the period of its exist- 

 ence ; but the time in which this takes place depends 

 upon the state of the weather and the nature of the soil. 



The annual is uniformly developed in all its parts ; 

 the food daily taken up is expended in increasing the 

 overground and underground organs, which meanwhile 

 take up a larger amount of food in proportion to the 

 increase of their absorbent surface. With the growth 

 of the plant, the conditions of increase inherent in the 



