DECOMPOSITION OF PLANTS. 



our garden. Some of the genera of plants appear 

 to have distinct agents assigned to them, and the 

 detection and enumeration of them have been car- 

 ried to considerable extent by some of the foreign 

 naturalists ; but, to point out the variety and curi- 

 ous organization of these substances, we will only 

 instance four, to be found on the common plants of 

 the garden or the copse : the laurel, the elm, the 

 sycamore, and the beech. 



The laurel (primus laurocerasus) is not, properly 

 speaking, a deciduous plant, though it casts its 

 leaves in considerable numbers during the spring 

 and summer seasons. These long resist the com- 

 mon agents of dissolution, like those of the holly, 

 by means of the impenetrable varnish that is spread 

 over them. This, however, wears off, and they 

 decay ; but their destruction is at times accelerated 

 by a small excrescent substance, which fixes on the 

 leaf, breaks the surface, and admits humidity. It 

 appears in the form of a small black speck, and, 

 when ripe, discharges a yellow powder from the 

 centre; but as soon as one speck, which is the 

 vessel containing the capsules, has fixed itself on 

 one side of the leaf, a similar one will be found im- 

 mediately opposite on the other ; and hence it is 

 well named by Lamarck the two-fronted uredo 

 (uredo bifrons) *. This I believe to be pecu- 



* Without close examination, this plant appears to be a uredo j 

 but it is in fact a sphseria. Uredo differs from spheeria chiefly in 



