390 VEGETATION OF THE CARBONIFEROUS PERIOD 



better preserved specimens retaining those organs and appendages which 

 the most skilful botanist requires to examine in the living vegetable 

 before he can pronounce decidedly on its affinities. The female flowers 

 or fruit are distinguishable in very few cases, and they are so rare 

 that but one genus of coal-plants has thereby been referred with any 

 certainty to its proper position in the natural system. They occur in 

 the form of cones (aggregations of seed-vessels) or of isolated seed- 

 vessels. Their form alone is generally preserved, their interior having 

 been wholly destroyed, or presenting a crushed and shapeless mass of 

 disorganized tissue. The solitary nuts, again, may have grown in 

 cones or separately : they have never been found attached nor in a po- 

 sition relatively to any leaf, branch, or cone, that would justify their 

 having belonged with certainty to either. Of male flowers no traces 

 remain. Leaves and scales occur abundantly, but almost invariably 

 detached, as is generally the bark of the stems or trunks, so that the 

 very outline of the vegetable is frequently lost. Hence arises the ne- 

 cessity, in the infancy of this science, of describing the different portions, 

 perhaps of one plant, as species, and of arranging them provisionally 

 into genera ; the word genus signifying, not a natural group of species, 

 but a set of organs ; and being synonymous in many cases with a 

 shorter and more expressive Latin word, long in use and better under- 

 stood. As an example, the genera Strobilites and Lepidostrobus may 

 be cited, whose species are various cones (strobili), in some cases of 

 Lepidodendron, in others possibly of other plants, widely different ; 

 even the order to which they belong being distinct from that including 

 Lepidodendron. 



This arrangement of portions of specimens under various genera is 

 highly detrimental to the progress of systematic botany, but is not 

 equally disadvantageous to the geologist, whose object it is to deter- 

 mine the relationship of strata, by means of a comparison of their 

 contained species, without so particular a reference to their affinities. 

 The identification of these is always open to question, from the errors 

 into which the imperfection of the specimens necessarily leads. Two 

 specimens of one plant, the one more perfect than the other, are 

 frequently described as different: this is eminently the case in the 

 Sigillarice, the markings upon the surface of whose bark differ from 

 those on the similar surface exposed by the removal of that bark, while 

 in many specimens it is exceedingly difficult to determine whether the 

 latter be present or not. The markings also vary extremely in 

 different parts of the same trunk ; insomuch that fragments which had 

 been regarded as characteristic of six or eight separate species, have 

 been more recently found to belong to one, that one presenting a sur- 

 face equal to those six or eight fragments collectively, whereon the 



