210 WITHERED LEAVES. 



by the aid of the revelations of the microscope ; but much may be 

 learned by their megascopic examination, or so much as may be 

 ascertained by the unaided eye, and to this we shall now address 

 ourselves. Taking up from the ground a few withered leaves 

 fallen from different trees, we shall perceive that all are not alike, 

 either in size, shape, or arrangement. In some, the petiole or leaf 

 stalk is long, in others short. The general shape and outline of 

 the leaves differ, and the arrangement of the ribs and veins are as 

 various as the leaves themselves. All these variations are indica- 

 tions, and miniature representations, of the trees on which they 

 grew. Thus the length of the petiole will indicate the compara- 

 tive height which the stem or trunk attains before it becomes 

 divergent in the branches ; and the venation will show the gene- 

 ral arrangement and angle of divergence of those branches, and 

 their sub-division into smaller branches, stems, and twigs. And 

 these, again, have their correspondence in the direction and rami- 

 fications of the roots. It would be interesting to stand for a few 

 minutes before some tree — say an oak, a beech, or an elm, — and, 

 leaf in hand, compare the course and ramifications of its ribs, and 

 veins, with the now leafless branches standing out in bold relief 

 against the grey wintry sky, and notice the strong resemblance 

 which exists between them. 



Not only do these reticulated veined leaves show us the gene- 

 ral outline of the trees on which they grew, but they are one of 

 the marks by which we learn that these trees are individuals in the 

 great family of Dicotyledons or exogenous plants, as distinguished 

 from the endogens or Monocotyledons ; and so take us back to 

 the earliest period of their independent existence. Thus we are 

 taught, that when the seed was cast into the ground, it germinated, 

 and thrust a fibrous rootlet downwards, while from the yielding soil 

 there appeared two or more green, fleshy, leaf-like opposite coty- 

 ledons. And then as growth proceeded, there rose a stem, which 

 subsequently became a trunk consisting of both cellular and vas- 

 cular tissue, a portion of the latter being elastic vessels, and com- 

 prising three parts, one within the other, viz., bark, wood, and 

 pith, and increasing by an annual deposit of new wood and corti- 

 cal substance between the wood and the bark ; hence we may 

 compute the age of an exogenous tree, by counting the number of 



