296 CALAMARIEAE. 



when, in consequence of the impulse given by Brongniart 1 , the fact of 

 the secondary growth of wood in the stems of Calamitae began to be 

 taken into account, opinions became at once divided. Brongniart himself 

 on elementary grounds, which we have already considered in the chapter 

 on Sigillariae, was entirely opposed to the assumption of a secondary growth 

 in thickness in archegoniate plants, and suggested the separation of Cala- 

 marieae into two groups, which belonging to quite different divisions of 

 the vegetable kingdom were supposed to show great resemblance to one 

 another only in the vegetative region. He was followed on this path not 

 only by his pupils, Renault especially and Grand' Eury 2 , but by Goppert 3 

 also and more recently by Schenk 4 . One of these groups, the Calamiteae, 

 was to include the fructifications of archegoniate character, together with 

 the impressions of stems belonging to them and also a portion of the casts ; 

 it was supposed to belong to the cycle of affinity of Equisetinae, and to 

 have no secondary growth. To the other group, that of Calamodendreae, 

 was assigned all the petrified specimens with secondary growth and a 

 corresponding number of impressions and casts, and these were referred to 

 Gymnosperms on account of the structure of their wood. Renault 5 has 

 recently inclined to connect them with Gnetaceae, and to look upon some 

 of the fossil carpoliths as their seeds. 



There is another group of authors, with Schimper G , Williamson 7 and 

 more recently Stur 8 at their head, who hold firmly to the belief that the 

 remains of Calamitae all belong to one division of plants, and see in them 

 a group allied to Equiseteae, and distinguished from them by the intro- 

 duction of secondary growth, just as Lepidodendron and Sigillaria are 

 distinguished from recent Lycopodiaceae. 



As the occasion for this difference of opinion came from the petrified 

 specimens, it will be well to take them first into consideration. In general 

 they are nothing more than the hollow cylinder of wood deprived of the 

 rind, and inclosing a broad medullary tube filled with the mineralising 

 matter. If the section has not passed directly through a node, it discloses 

 a perfectly regular circle of wedges of wood. Each of these wedges ter- 

 minates on the side of the pith in a sharply projecting primary bundle, 

 the transverse section of which may vary much in its form, and in the inner 

 angle of the bundle there is usually a roundish irregularly defined lacuna, 

 which has often been taken for the analogue of the carinal canal of Equi- 

 setae. The lacuna is usually bounded on the inside by a group of elements 

 with rather broad lumen, and these are succeeded by any parenchyma-cells 

 which still persist in the periphery of the medullary tube. In some rare 



1 Brongniart (2), p. 97. a Grand' Eury (1). 3 Goppert (3). 4 Schenk (2), 



and Zittel (1). 5 Renault (2), vol. iv, p. 215. 6 Schimper (1). 7 Williamson (1). 



* Stur (8). 



