THE CARBONIFEROUS FLORA. 



163 



continued vitality of the bark is shown by the occasional production 

 of lateral strobiles on large branches, in the manner of the modem 

 red pine of America. In other species the arcoles neither increase in 

 size nor become regularly separated by growth of the intervening 

 bark ; but in old stems the bark splits into deep furrows, between 

 which may bo seen portions of bark still retaining the areoles in 

 their original dimensions and arrangement. This is the case with 

 Jj. Pictopn.ie. This cracking of the bark no doubt occurs in very old 

 trunks of the first two types, but not at all to the same extent. 



As a type of Lepidodendron, 1 may describe one of the oldest 

 Carboniferous species characteristic of the Lower Carboniferous in 

 America, and corresponding to L. Ydtheimianum of Kurope. 



LEPrDODE>fDRON CoRRuoATUM, Dawson. — (See Fig, 4:5, snjrrn.) 

 " Quarterly Journal of Geological Society," vol. xv. ; " Acadian Geol- 

 ogy," page 451. 



Habit of Orowth. — Somewhat slender, with long V)ranches and 

 long, slender leaves having a tendency to become horizontal or 

 drooping. 



Markings of Stem. — Leaf-bases disposed in quincunx or spirally, 

 elongate, ovate, acute at both ends, l)Ut more acute and slightly 

 oblique at the lower end ; most prominent in the iq)per third, and 

 with a slight vertical ridge. Leaf-scars small, rounded, and showing 

 only a single punctiforin vascular scar. The leaf-scar on the outer 

 surface is in the \q)per third of the base; but the obliquity of the 

 vascular bundle causes it to be nearly central on the inside of the 

 epidermis. In young succulent shoots the leaf-scars are contiguous 

 and round as in Cyclostigma, without distinct leaf-bases. In this 

 state it closely resembles L. Olivieri, Kichwald.* 



In the ordiiuiry yoimg branches the leaf-si ars are contiguous, 

 and closely resemble those of L. ehgann, IJrongt. (Fig. 43 C). As the 

 branches increase in diameter the leaf-scars slightly enlarge and 

 sometimes assume a vcrticillate appearance (Fig. 413 D). As they 

 still furtluir enlarge they become scpiinittMl by gradually increasing 

 spaces of bark, marked with many waving stritc or wrinkles (Fig. 

 43 I, N). At the base of old stems the bark assumes a gfjni'rally 

 wrinkled appearance without distinct scars. 



Kiwrria or Decorticated States. — Of these there is a great variety, 

 depending on the state of preservation, and the particular longi- 

 tudinal ridges. Fig. 43 I) shows a form in which the vascular bun- 

 dles appear as cylindrical truncate projecti'-ns. Other forms show 



* Lethaea Rossica, Plato Y, Figs. 12, 18. 



^ 'rW 



