THE FLORA OF THE COAL FORMATION. 431 



largely to the production of coal. Let us take as an example of them 

 a species very common at the Joggins, and which I have named S. 

 Brownii^ in honour of my friend, Mr R. Brown of Sydney. Imagine 

 a tall cylindrical trunk spreading at the base, and marked by perpen- 

 dicular rounded ribs giving it the appearance of a clustered or fluted 

 column. These ribs are marked by rows of spots or pits left by fallen 

 leaves, and toward the base they disappear, and the bark becomes 

 rough and uneven, but still retains obscure indications of the leaf-scars, 

 widened transversely by the expansion of the stem. At the base the 

 trunk spreads into roots, but with a regular bifurcation quite un- 

 exampled in modern trees, and the thick cylindrical roots are marked 

 with round sunken pits or areoles, from which spread long cylindrical 

 rootlets. These roots are the so-called Stigmarice, at one time regarded 

 as independent plants, and, as the reader may have already observed, 

 remarkable for their constant presence in the underclays of the coal- 

 beds. Casting our eyes upward, Ave find the pillar-like tnnik, either 

 quite simple or spreading -by regular bifurcation into a few thick 

 branches, covered with long narrow leaves looking like grass, or, more 

 exactly, like pine leaves greatly increased in size, or, more exactly still, 

 like single leaflets of the leaves of Cycads. Near the top, if the plant 

 were in fruit, we might observe long catkins of obscure flowers or strings 

 of large nut-like seeds, borne in rings or whorls encircling the stem. 

 If we could apply the woodman's axe to a Sigillaria, we should find 

 it very different in structure from that of our ordinary trees, but not 

 unlike that of the Cycads, or false sago-plants of the tropics. A 

 lumber-man would probably regard it as a tree nearly all bark, Avith 

 only a slender core of wood in the middle ; and, botanically, he would 

 be very near the truth. The outer rind or bark of the tree Avas very 

 hard. Within this Avas a very thick inner bark, partly composed of a 

 soft corky cellular tissue, and partly of long tough fibrous cells like 

 those of the bark of the cedar. This occupied the greater part of the 

 stem cA'en in old trees four or five feet in diameter. Within this Ave 

 Avould find a comparatively small cylinder of Avood, not unlike pine in 

 appearance, and even in its microscopic structure ; and in the centre a 

 large pith, often divided, by the tension caused in the growth of the 

 stem, into a series of horizontal tables or partitions. Such a stem 

 Avould have been of little use for timber, and of comparatively small 

 strength. Still the central axis of Avood gave it rigidity, the surround- 

 ing fibres, like cordage, gave the axis support, and the outer shell 

 of hard bark must have contributed very materially to the strength 

 of the Avhole. Growing as these trees did in swampy flats close 

 together, and the bark of which they were chiefly composed being less 



