ROOTS AND ROOTLETS. 35 



Plate XIII, fig. 64, is an inorganic cast of the medullary cavity of a Stigmaria, 

 from the Hutton Collection, now in the Museum of the Natural History Society of 

 Newcastle-upon-Tyne. The figure is of the natural size. The diagonal rows of 

 oblong ridges covering the surface of the specimen are casts of the medullary ends 

 of the primary medullary rays of the vascular cylinder. 



vascular bundles given off from the axial vascular cylinder of Stigmaria. Whether we examine trans- 

 verse sections of that cylinder (Plate VII, fig. 14,/), longitudinal radial sections (Plate VI, fig. 9,/), 

 tangential sections (Plate V, fig. 8), we arrive at the same conclusion. We find a number of vascular 

 bundles, springing from the vascular cylinder of the axis, in a uniformly characteristic manner. All 

 these bundles pass outwards, through the primary medullary rays specially provided for their trans- 

 mission, in a geometric order, which is not more disturbed by slight irregularities of growth than is the 

 case with the equally geometric phyllotaxis of recent leaves. When these vascular bundles emerge from 

 the cylinder, to pass through the bark, they all bend downwards (Plate XII, figs. 37 and 39) in true root- 

 like fashion and which is the reverse of the course pursued by all the leaf bundles of Lepidodendroid 

 branches. On emerging from the outer bark, with the exception of an occasional derangement, resulting 

 probably from the arrested development of some rootlet when in a very young state, the quincuncial 

 arrangement of these rootlets in diagonal lines again becomes geometric. Turning to the structure of 

 the rootlets, whose origin and course alike illustrate vegetative repetition in one of its most mechanical 

 forms, we find that they display no material variation in the structure that is so characteristic of them. 

 The rootlet bundle is invariably monarch in its orientation ; its point of orientation is always acropetal 

 in relation to the growiog root upon which each rootlet is planted. 



In the face of facts like these, still to insist that structures, which are so obviously vegetative 

 repetitions of one another, develop into a confused medley of rootlets and leaves, has no claim to rank 

 as a scientific inference. It becomes a mere preconceived idea adhered to in the face of an over- 

 whelming array of opposing facts. 



Unfortunately the mischief does not end here. What I have given my reasons for regarding as 

 errors of observation have led M. Renault to other conclusions equally unjustified by any known facts. 



In his ' Cours de Botanique ' he has a paragraph headed "Mode de Croissance des Sigillaires " 

 (loc. cit., pp. 102, 163, 164). I regard this paragraph as full of unsupported hypothetical statements. 

 All our experiences in Great Britain, Canada, and the United States, in each of which countries 

 Sigillarian and Lepidodendroid stems with Stigmarian roots are abundant, give to these hypotheses 

 an unqualified contradiction. No solitary instance can be shown in any of these countries in which 

 " l'extremite d'une branche de Stigmaria se relevait en bourgeon aerien." Even Brongniart tells us of 

 " l'absence de toute apparence d'un bourgeon terminale " (' Tableau des Genres de Vegetaux fossiles,' 

 p. 56). It is unfortunate for science that M. Renault should hold such views unless he could support 

 them by more conclusive proofs than he has hitherto recorded. When we find these views receiving the 

 degree of countenance and circulation which MM. Saporta and Marion have given to them in their 

 recent work, ' L'Evolution du Regne Vegetale,' the matter becomes still more serious. It is the 

 support thus given to these retrograde opinions that in 1883 led Sir William Dawson to say, half 

 despairingly, in his address to the American Association for the Advancement of Science, " Some one 

 will have to rescue from total ruin the results of our labours." 



I claim no monopoly of the knowledge of what is true ; but I am entitled to ask that when a 

 considerable number of practised observers, after many years of careful investigation, arrive at certain 

 definite conclusions, those conclusions should not be lightly disturbed. To justify such a course, the 

 disturber should be prepared with such strong evidence as very definite facts alone can furnish. Such 

 facts, I contend, M. Renault has not yet laid before us. In their place we have only got opinions ! 



