

242 BOTANICAL GAZETTE [march 



Leaf size in plant geography. — Rauskiaer, 4 whose name is associated 

 with the system of biological types or life forms, has recently submitted another 

 means of quantitative estimation, so far as the unit chosen is a recorder of the 

 biological value of a climate. He regards the size of the leaf as the outstand- 

 ing character, and using the simple leaf as a standard, has proposed a system 

 of leaf classes (Bladst^rrelsesklasser). In the plan submitted there are 6 

 different classes or divisions: (i) leptophyll, 25 sq. mm.; (2) nanophyll, • « 



9X25 = 225 sq. mm.; (3) microphyll, 9^25 = 2025 sq. mm.; (4) mesophyll, 

 9^X25 = 18225 sq. mm.; (5) macrophyll, 9^X25 = 164025 sq. mm.; (6) mega- 

 phyll, which is limited by the upper limit of macrophylls. Originally he 

 planned to use the number 10 with 25, but from a large number of trials, both 

 by himself and several of his colleagues, 9 was found to give a better differ- 

 entiation. In using 9, it is easy to make subdivisions, large, medium, and 

 small, if desired. Raunkiaer is of the opinion that it is an easy matter to 

 place the various leaves in their right classes, but in order to facilitate matters, 

 a graphical representation of the various limits of surface area is pictured, 

 and by the use of this scheme the leaves may be correctly grouped. Thus, if 

 a leaf has an area which is less than 25 sq. mm., it is a leptophyll; if larger 

 than 25 sq. mm. but smaller than 225 sq. mm., it is a nanophyll, and so on. 



In using such a method, Raunkiaer contends that it is possible to obtain 

 the biological factor for climate as far as it influences leaf size. By the use of 

 such a scheme, comparisons may be made readily between two climates which 

 have varying effects. One may compare formations which vary at different 

 points, and also determine the relation between a series of associations which 

 are somewhat similar. To prove his point he has selected and analyzed 

 several European evergreen shrub formations. 



He suggests that the leaf "size classes" are not the only quantitative units 

 to be employed, but shows that these units lend themselves rather readily to 

 the statistical method. A system which would in some way estimate such 

 structural features as stomatal protection, stomatal opening, or hairiness, 

 would also give significant results. The difficulties would naturally be many, 

 but they should not hinder the attempt. 



Ecologists and physiologists no doubt will be in hearty sympathy with 

 Raunkiaer's move in placing ecology upon a basis that is at least somewhat 

 quantitative. We all are in accord with his concluding sentence (translated 

 somewhat literally): "by such means only will it be possible to pass beyond 

 the tourist plant geographer's superficial and vague determinations." — A. L. 

 BakkeJ 



Mountain grassland. — Many of the valleys of the Colorado Rocky Moun- 

 tains have their comparatively level floors covered with grasslands of somewhat 



« Raunkiaer, C, Om Bladst0rrelsens Anvendelse i den biologiske Plante- 

 geografi. Botanisk Tidsskrift 34:225-240. 1916. 





