EESULTS OF PAL^ONTOLOGICAL RESEARCH 67 



(1) The Law of Specialization (Differentiation). 



(a) The Calamariacese Series. 



In the Devonian formation, probably already in 

 strata which may be ascribed to the Silurian period, 

 there are found the first remains of Equisetse the so- 

 called Protocalamariacese. In the upper productive 

 coal formations these primary Equisetse become Cala- 

 mariacese. How did that occur ? The Protocalamari- 

 aceae show clearly, in the stone kernels preserved, the 

 impressions of the main vein fascicles running upwards 

 in the stem in the form of longitudinal furrows (Fig. 19) 

 which, as opposed to those of the Calamariaceae in the 

 separate nodes of the stem, lie exactly in line with 

 each other ; in the Carboniferous forms, on the other 

 hand, each furrow ends between two of the furrows of 

 the upper node. Now it can be accepted as quite 

 certain that this alteration had a definite purpose 

 because, as Haberlandt in his excellent work 1 points 

 out, the formation, position, and direction of the vas- 

 cular bundles stand in the closest possible relation to 

 the physiological needs. To what new life conditions 

 these old Equisetse conformed thereby we naturally 

 cannot say with our present knowledge. This question 

 can only be solved by constant consideration of the 

 present ' adaptive evidence/ 



If we now consider that the Protocalamariaceoe 

 groups only occur in the oldest strata of the coal 



1 G. Haberlandt : Physiologische Pftanzenanatomie, Leipzig, 1909, p. 338, 



F2 



