ANOMALOUS THICKENING IN DICOTYLEDONS AND GYMNOSPERMS. 569 



usually connected with the appearance of new zones of intercalary wood, bast, and 

 cambium derived from secondary meristem : Sects. 193, 194. 



All these chief phenomena often show not only reciprocal approaches to one 

 another, but often occur variously combined. The following description of con- 

 crete instances is arranged as nearly as may be according to the above heads, 

 but cannot be classified exacdy in that way, without relinquishing all clearness, 

 and incurring endless repetition. The paragraphs specified under the single heads 

 usually indicate those points only where the mosl important examples of them are to 

 be found. 



The consequences of increase in thickness as they affect the changes of the 

 peripheral parts, dilatation, distortions, secondary metamorphoses in the cortex, and 

 formations of periderm, are in general the same, and varied in the same manner 

 in anomalous stems as in normal secondary thickening. They have been but little 

 investigated in detail. They will therefore be only shortly noticed as opportunity 

 offers in the following description. 



Where cambium and bundles of wood and bast develope from secondary 

 meristem, the latter always arises by division of parenchymatous cells, which are as 

 usual for the most part relatively short, while the above-named tissues are composed 

 of elongated elements. Those secondary formations must therefore induce distortion 

 and displacement of the tissues present. With the exception of the one case, to be 

 noticed below, of Cocculus palmatus, investigated and discussed by Radlkofer, 

 Nageli, and Eichler, no exact investigation has been made of these phenomena. 



As is the case with almost all anatomical peculiarities the anomalies of secondary 

 thickening also are in part evident phenomena of adaptation, and may in part even be 

 explained directly as the outcome of mechanical causes ; they are in part unexplained 

 anatomical characters, which must be regarded as inherited. To the first category 

 belong the anomalies of twining and climbing liane-stems from the most different 

 families, whose non-climbing congeners have normal growth, as in the Bignoniaceae, 

 Sapindacea2, Leguminosse, Malpighiaceae, and others to be named below. The 

 lianes from certain families, especially the Sapindaceae, or at least the majority of 

 them, show very special peculiarities. On the other hand, a remarkable uniformity 

 is often seen between those belonging to the most different families, as e. g. Meni- 

 spermum and Gnetum, Bignonia and some Apocynaceae, &c. To the second category 

 of unexplained anatomical characters belong the phenomena to be described in the 

 Chenopodiaceae and their allies, in Strychnos, Avicennia, &c. It is sufficient to refer 

 shortly to this, and to dispense with further observations, till exact investigations of 

 individual cases have been published. 



Sect. 182. As the first and simplest instance of anomalous distributiojt of tissues 

 where the cambium is normal may be mentioned the case, in which the production of 

 wood alongside of the latter is unequal in successive longitudinal bands, while the 

 production of bast is more active opposite those bands where the development of 

 w'ood is less. The wood, therefore, when considered separately, appears excentrically 

 unequal in some definite form, or furrowed, in transverse section notched and lobed. 

 The eccentricity is, however, equalised, and the furrows filled up by correspondingly 

 large and specially formed masses of bast, and the whole form of the stem or root 

 differs from that of the wood. Leaving cases of very slight inequality out of account, 



