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 modern 

 red pine of America. In other species the areoles 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 be seen portions of bark still retaining the areoles in 

 their original dimensions and arrangement. This is the case with 

 L. Pictoense. 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, I may describe one of the oldest 

 Carboniferous species characteristic of the Lower Carboniferous in 

 America, and corresponding to L. Yeliheimianum of Europe. 



Lepidodendron Corrugatum, Dawson. — (See Fig. 43, supra.) 

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

 ogy," page 451. 



Habit of Growth. — Somewhat slender, with long branches 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, but more acute and slightly 

 oblique at the lower end ; most prominent in the upper third, and 

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

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

 surface is in the upper 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, Eichwald.* 



In the ordinary young branches the leaf-scars are contiguous, 

 and closely resemble those of L. elegans, Brongt. (Fig. 43 C). As the 

 branches increase in diameter the leaf -scars slightly enlarge and 

 sometimes assume a verticillate appearance (Fig. 43 D). As they 

 still further enlarge they become separated by gradually increasing 

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

 43 I, N). At the base of old stems the bark assumes a generally 

 wrinkled appearance without distinct scars. 



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

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

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

 dles appear as cylindrical truncate projections. Other forms show 



* Lethaea Rossica, Plate Y, Figs. 12, 13. 



