74 LYCOPODIALES [OH- 



Lepidodendron by the power of forming secondary vascular 

 tissues; the latter genus, originally thought to be always 

 herbaceous, was classed with the Pteridophytes. At the time 

 when this unnatural separation was made between stems with 

 secondary wood and those in which no secondary wood was 

 known to exist, botanists were not aware of the occurrence of 

 any recent Pteridophyte which shared with the higher plants 

 the power of secondary growth in thickness provided by means 

 of a meristeraatic zone. It is true that the presence or absence 

 of a cambium does not in practice always coincide with the 

 division into herbaceous and arborescent plants : no one would 

 speak of a Date-Palm as a herbaceous plant despite the absence 

 of secondary wood. 



The danger which should be borne in mind, in adopting as a 

 matter of convenience the term herbaceous as a sectional 

 heading, is that it should not be taken to imply a complete 

 inability of the so-called herbaceous types to make secondary 

 additions to their conducting tissues. The specimens on which 

 the species of Lycopodites and Selaginellites, (genera which 

 may be designated herbaceous,) are founded are preserved as 

 impressions and not as petrifications ; we can, therefore, base 

 definitions only on habit and on such features as are shown 

 by fertile leaves and sporangia. We are fully justified in 

 concluding from evidence adduced by Goldenberg more than 

 fifty years ago and from similar evidence brought to light by 

 more recent researches, that there existed in the Palaeozoic era 

 lycopodiaceous species in close agreement in their herbaceous 

 habit with the lycopods of present-day floras. It has been 

 suggested' that the direct ancestors of the genera Lycopodium 

 and Selaginella are represented by the species of Lycopodites 

 and Selaginellites rather than by Lepidodendron and Sigillaria, 

 the arborescent habit of which has been rendered familiar by 

 the numerous attempts to furnish pictorial reproductions of a 

 Palaeozoic forest. Until we are able to subject the species 

 classed as herbaceous to microscopical examination we cannot 

 make any positive statement as to the correctness of this view, 



1 Halle (07) p. 1. 



