iSje. 



IS STIGMARIA A ROOT OR A RHIZOME? 365 



II. 



A REPLY TO MR. HICK. 



I fully agree with Mr. Hick when he intimates that morpho- 

 ogical considerations have an equal, or even a greater value, 

 than physiological, when endeavouring to ascertain the true nature 

 of Stigmaria ficoides. But while admitting this, I am not prepared to 

 follow him in appealing too strongly to conditions now found among 

 living plants, and pushing them too far when endeavouring to explain 

 the very different combinations that so abundantly present them- 

 selves among the Palaeozoic forms. At that period no Angio- 

 sperms existed on the earth, and even the Gymnosperms were very 

 far from reaching their modern development. Under these circum- 

 stances, the Cryptogams chiefly became the giant forest-trees of 

 that remote age. To become such, they required an organisation 

 very different in some respects from that of their degraded living 

 representatives. Hence, we must not appeal to these degenerate 

 types for illustrations and explanations of structures no longer 

 existing. Still less must we turn to what we find in the Angiosperms, 

 that wholly distinct race which has taken the place of the primaeval 

 Cryptogams in our woods. 



The primaeval giants of the swampy forests had doubtless a 

 morphology assigned to them adapted to the physical conditions by 

 which they were surrounded, but if even their dwarfed and other- 

 wise modified descendants fail to throw light upon morphological 

 details once so common, still less must we expect to obtain that 

 light from the living and wholly different flowering plants. In this 

 respect the via media is the safest. That these modern forms are in 

 some line or other descended from the primaeval types is accepted by 

 every Darwinian. Hence, while we accept from the former any 

 light that they can throw upon peculiarities in the latter, we must 

 not deny that those peculiarities were real because they are no 

 longer to be found among living plants. 



The question before us seems, at the first glance, to be a very 

 simple one, but it is less so than it really appears to be. Are our 

 British forms of Stigmaria roots or rhizomes ? We are soon involved 

 in difficulties unless we disputants are agreed upon the sense in which 

 we employ these two terms. To be certain on this point, I have 

 selected the definitions of a rhizome given by Sachs, by Maout and 

 Decaisne, and by Henfrey. 



Sachs says : " It is of very common occurrence with Cryptogams 

 and Angiosperms for a persistent primary axis or branch-system to 

 continue to grow underground, and to send up only at intervals long 



