May. i893. THE FRUIT-SPIKE OF CALAMITES. 355 



is only partially given. Among other details, however, it is stated 

 that the axis had " a bundle of fine scalariform tissue in its centre, 

 forming about a third of its diameter, and generally appearing free 

 from the surrounding cellular tissue, which is composed of somewhat 

 •elongated cells." 



Throughout his description, Carruthers appears to have had no 

 doubt whatever that he was dealing with the fruit of Catamites. In 

 this he was probably guided by the great and undoubted similarity 

 •of the general characters of the spike to those of Eqidsetmn, with 

 which Calamites has always been held to have a close relationship. 

 At any rate, he does not seem to have considered that the anatomy 

 of the axis as he then understood it, i.e., with scalariform tissue, 

 and not parenchyma, in the centre, was an insuperable difficulty in 

 the way of a determination supported by so many of the other 

 characters of the spike. 



Binney's description of Calamostackys Binneyana was published in 

 1868, and though his account is very unsatisfactory from the 

 botanist's point of view, it implied the presence of a vascular bundle 

 in the centre of the axis, as described by Carruthers. In spite of this, 

 he accepted the view that the affinities of the spike were with 

 Calamites, and does not seem to have considered it necessary to explain 

 •on this assumption the presence of the axile vascular strand. 



In 1 87 1 Williamson began that series of memoirs on " The 

 Organisation of the Fossil Flora of the Coal-measures " which have 

 ■done so much to increase our knowledge of Carboniferous plants. 

 The first of these deals with Calamites, and incidentally the question 

 •of its relationship to Calamostackys Binneyana is referred to. It is 

 pointed out (5) that in Calamites the centre of the stem is occupied by 

 a purely cellular pith with a vascular zone at its periphery, while in 

 Calamostackys Binneyana these conditions are reversed. Hence the 

 inference is drawn that if the latter be the fruit-spike of the former, 

 then in passing from one to the other the tissues must undergo a 

 metamorphosis which is without parallel among living plants. In 

 the fifth memoir (1874) the spike is described afresh, and many 

 new details of structure are given with respect to it. Discussing its 

 affinities in the light of the fuller knowledge, the author says (6) : — 



" After balancing these various facts and arguments, I am led to 

 the conclusion that Calamostackys Binneyana has much closer affinities 

 with Asteropkyllites than with Calamites. With the latter it has no one 

 feature in common. There is no solitary point in which the two 

 plants resemble each other. The resemblance of the fertile sporangia 

 of Calamostackys to those of Eqnisetum has been combined with the 

 foregone conclusion that the Calamites were Equisetaceous plants, in 

 leading to the belief that the two were parts of the same plant ; but I 

 cannot conceive of any conditions in which the stem of a Calamite 

 could be prolonged into that of a Calamostackys. I have carefully 

 investigated the relations which the fertile stems of the Equiseta bear 

 to axes of their terminal fruit-spikes, and I find that their respective 

 structures are typically identical. The transition from the stem to 



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