326 THE AMERICAN MONTHLY [Oct., 



a water-proof outer covering to prevent the loss of the 

 water of the cells and to obtain some form of supporting 

 material to enable it to spread out in the air a consider- 

 able surface, and yet one strong enough for support un- 

 der all contingencies. The requirements of this problem 

 are variously met in all plant leaves, in each kind in a 

 slightly different way. Our present study is designed to 

 show how the problem is solved in the case of the ger- 

 anium. 



The leaf of the geranium is long-petioled, palmately- 

 netted veined, cordate at the base, crenately rounded 

 and lobed, its surface pubescent. An examination shows 

 that the strong and flexible material of the stem is con- 

 tinued out onto the broad blade in the form of several 

 large and innumerable smaller lines called "veins." 

 These run to every part of the structure and form a 

 frame-work for the support of the softer material be- 

 tween. At the margin, minute divisions of the veins can 

 be traced to the lobes and still finer ones to their sub- 

 divisions. If the veins of the leaf were to be preserved 

 and the rest removed, the shape of the organ would not 

 be altered in any respect. Besides the supporting frame- 

 work, the surface of the leaf presents a finely hairy ap- 

 pearance, almost deserving the name "velvety." This 

 is true of both the upper and the under surface and also 

 of the petiole or stem of the leaf. There is a difference 

 in the shade of the two sides of the leaf, the under be- 

 ing somewhat lighter than the upper surface. 



After determining these facts, one has a suggestion for 

 studies in the structure of the leaf. He will need to find 

 out what is the cause of the difference in color of the two 

 sides, also how the hairs are made and the structure of 

 the veins. All these facts cannot be ascertained in the 

 same way, but is quite obvious that a good deal ought to 

 be shown by an end view or section of the leaf. Such 

 a view is shown in figure 1. This is made by cutting off 



