480 SCIENCE PROGRESS. 



to be the common property of considerable groups of 

 plants. 



For example, the appearance of extrafascicular cambium, 

 resulting in the formation of successive rings of bundles, in 

 certain Leguminosae and Menispermaceae, and in Antigonum 

 among the Polygonaceae, is presumably a relatively recent 

 adaptation, correlated with the climbing habit ; extrafascicu- 

 lar cambium in Amaranthaceae, however, is a family char- 

 acter, acquired at some long past epoch and no longer of 

 obvious adaptive value. The inherited character has, 

 however, been somewhat further developed in some mem- 

 bers of the familv which have become climbers. Here an 

 " inherited" character has again become adaptive. On the 

 other hand we sometimes find a member of a climbing order, 

 which is not itself a climber, and yet has anomalous struc- 

 ture. This is the case with Cocadus laurifolius (28, p. 64), 

 a Menispermaceous tree, which has concentric rings of 

 bundles. If, as Schenk suggests, this plant is descended 

 from climbers, it affords a good example of a purely 

 adaptive modification which has become an inherited 

 anatomical character. 



Schenk's book is full of interesting details, which, unfor- 

 tunately, there is no space to discuss. 



It is superfluous to make any apology for the obvious 

 incompleteness of this article. Only a small part of the 

 field of internal morphology has been touched on at all, and 

 that only in the most cursory manner. It is hoped, how- 

 ever, that enough has been said to show that the study of 

 the internal structure of plants, if freed from the grooves of 

 mere description, and carried on from the point of view of 

 descent and adaptation, is likely to yield just as valuable 

 results as that of external morphology. 



BIBLIOGRAPHY. 



(1) De Bary. Comparative Anatomy of the Phanerogams and 



Ferns, English translation, 1884. 



(2) HABERLANDT. PJiysiologische Pflanzenanatomie, 1884. 



(3) STRASBURGER. Histologische Beit rage, bd. iii., 1891. 



