658 



HISTORY OF THE VEGETABLE KINGDOM. 



to have been intemiediate between the coniferae 

 nnd the lycopodiacete. They are very common 

 both in the coal seams, and in the accompanying 

 sandstones of the coal measures, and stems, from 

 20 to 45 feet in length, are frequently met with 

 in the north of England. " In coniferse," says 

 Professor Lindley, " the leaves are arranged upon 

 the stem in two very different waj^s: First, in tlie 

 species having what botanists denominate fasci- 

 cled foliage, such as the Scotch fir, the pinaster, 

 and Weymouth pine; the first leaves that are 

 developed, are brown and membranous, roll back, 

 and wither away, almost immediately after tlie 

 young branch has acquired its firstgrowth. From 

 the axilla of each of these sprouts forth a bud, 

 which never or rarely elongates, but which pro- 

 duces several leaves, the outermost of which are 

 membranous, and perishable like the first ; but 

 the innermost, narrow and rigid, forming the 

 permanent green foliage of the species ; in those 

 where the foliage has fallen away, the stem is 

 covered with numerous narrow projections, 

 thickest at the upper end, where tlie remains of 

 withered leaves are visible, arranged spii-ally with 

 great symmetry, and separated by intervals usu- 

 ally equal at least to twice the breadth of the 

 projections. Secondly, in the species in which 

 the leaves are solitary, as in the spruce, fir, and 

 araucaria, the leaves that arc originally developed 

 when the young shoot forms, never undergo any 

 material alteration, but are those which subse- 

 quently become the green foliage of the plant; 

 none, or few apparent axillary buds are develop- 

 ed ; and finally, the leaves either separate by a 

 clean scar of a rhomboidal or a roundish figure, 

 with a depressed point in its middle, where the 

 vascular bundle connecting the stem and leaf was 

 liroken througli, or separate imperfectlj^, leaving 

 behind an in-egular mark upon a rhomboidal 

 areola. The yew is an instance of the former, 

 the araucaria of the latter. In all cases, the 

 scars on the rhomboidal areoliE are disposed in a 

 spiral manner, with the most exact symmetry. 

 With coniferous plants of the latter kind, lyco- 

 podiaceae accord so much in the arrangement of 

 their leaves, and consequently in the appearance 

 of the surface of the stems after the leaves have 

 fallen, that it would be difficiilt to point out any 

 difference, except that they are often, as in fyco- 

 podium clavatum, rigidum, divaricatum, a less 

 spiral, having a tendency to become verticillate. 

 Lepidodendron accord equally with coniferie and 

 lycopodiacete, in the arrangement of the scars of 

 the leaves. 



The foliage of certain coniferos, such as arau- 

 caria and of lycopodiacese, is so similar, that 

 their casts would be scarcely distinguishable, 

 except by the larger size of the former. Lepido- 

 dendra accord better with coniferie than with 

 lycopodiacete in this respect. The ramifications 

 of coniferse and lycopodiacete are essentially dif- 



ferent. In the former, the branches arise from 

 the same place, on opposite sides of the main 

 stem, often assuming a vei'ticillate arrangement. 

 In the latter, the branches bifurcate whenever 

 a new bud is brought into action, so that the 

 whole of the divisions are dichotomous, and the 

 same takes place in the inflorescence whenever 

 the latter is composed, as in L. plilegmaria. 

 Hence, lepidodendra are more related to lycopo- 

 diacese than to coniferte in their manner of 

 branching; and as dichotomous ramifications are 

 extremely rare in recent plants, this circum- 

 stance, taken together with their other charac- 

 ters, strengthens M. Brongniart's opinion of their 

 strong analogy with lycopodiacea;. The tex- 

 ture and size of lycopodiacete and coniferte are 

 very dissimilar. The former are soft cellular 

 plants, with small, creeping, or erect stems, no 

 bark, and an imperfect formation of a woody 

 axis; the latter are large trees with a thick bark, 

 and a hard woody centre, which is incapable of 

 compression by any ordinary force. With nei- 

 tlier tribe do lepidodendra agree in these points; 

 they resemble lycopodiacete in their soft stem; for 

 specimens some inches in diameter are found so 

 compressed, as to be nothing more than a thin 

 plate; but they agree with coniferse in the size 

 they seem to have attained, and in the presence 

 of bark, although that part is thin compared 

 with the bark of recent coniferte. 



There are several species of lepidodendron hav- 

 ing distinct characters. 



Lepidodendron selaginoides has circular scais, 

 and short compactly imbricated leaves. 



L. ohovatum, with obovate areoliE, with a 

 rounded apex, a tapering base, the central ridge 

 even and undivided, and the scar at the apex of 

 the areolte bounded by a nearly circular outline. 

 Large specimens are found on the continent and 

 in Britain, in the coal seams, some 45 feet long, 

 and 4^ feet in diameter. 



L. elegans, scars similar to L. Sternbergii, but 

 the leaves much smaller and more delicate, and 

 the branches more slender and delicate. 



231. 



a Cnrdiocarpum acutum. 6 Lppidostrobus pinaster. 



Lepidostrobus oruatus. 



Caediocahpum acutum. (Fig. a, cut 231,) 

 found in groups in the shale from the Jarrow 

 colliery, Newcastle. Each grain is lenticular, 



