2 HICK : OUR KNOWLEDGE OF THE YORKSHIRE CALAMITY. 
minute structure and internal organisation on which most questions 
of affinity depend, can only be learnt from those petrifactions in 
which such structure has been preserved. As in the past so in the 
future, Calamitw with structure will be the safest guides to their 
affinities and organisation, while for the construction of the phylo- . 
genetic tree of the vegetable kingdom their aid will be absolutely 
indispensable. 
As is usually done in dealing with recent plants, it will be well 
to consider the various members of the Calamitw in their natural 
order, beginning with the roots and then passing on successively to 
the stems, leaves, and reproductive organs. 
Roots and Rootlets. 
Of the roots and rootlets of the Calamitw little appears to be 
known. From statements made by Binney* it would seem that in 
the genus Calamites both roots and rootlets were present. Of tbe 
former he says, "the termination of the root of a Calamite is exactly 
of the same form as the terminal part of a Stigmaria, both being 
club-shaped"; and of the latter, that "they very much resemble the 
rootlets of Stigmaria, if they are not identical with them," and are 
''arranged in regular quincunical order." 
Adventitious roots were given off from the nodes of the aerial stem • 
at the tapering basal part and from the figures given in the literature, 
they appear to have been slender, cylindrical, and sometimes branched 
structures, the branching being apparently dichotomous. According 
to Solms-Laubacht some species of Calamitw had subterraneous 
rhizomes which likewise gave off roots from the nodes, often crowded 
together in tufts, and which when seen in impressions, had the form 
of long usually simple ribbon-like stripes. 
Looking at those statements critically, one can scarcely avoid 
the suspicion that the quincunical arrangement of the rootlets 
mentioned by Binney requires further investigation. There is no 
case known among existing plants where such an arrangement of 
* Observations on the Structure of Fossil Plants found in the Carboniferous 
Strata. I. Calamites and Calamoclendron, 1868, Palaeontographical Soc. 
t Fossil Botany. Eng. Ed. , pp. 308, 309. 
