ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 593 



The radical bundles are always three in number, one median inferior 

 and two lateral, placed symmetrically on tlio lower half of the net- 

 work. The lower radical bundle always springs from the upper 

 extremity of a vertical bundle of the stem, inserted on its outer side, 

 almost always exactly in the middle, and often a little lower than the 

 medio-dorsal foliar bundle. From this point it rises obliquely in the 

 cortex, and after passing from 5 to 7 mm. bends, becomes thinner, 

 and goes out at the base of the petiole with the roots of which it 

 forms the central cylinder. 



This inferior radical bundle is almost always absolutely inde- 

 pendent, but this is not always the case with the lateral radical 

 bundles. These latter have often a common point of departure with 

 the lower lateral foliar bundles, to which they may adhere for a 

 longth varying from 2 to 4 mm. ; but the portion of this common 

 base which belongs to the radical bundle is generally clearly to be 

 distinguished from that which belongs to the foliar bundle, and some- 

 times the two bundles are altogether distinct from their insertion. 

 These lateral roots behave differently from the inferior root ; after 

 an oblique course they pierce in the same way the cortex of the 

 petiole, the superficial layers of which form a cushion round their 

 base. 



The examination of other ferns confirmed the view that in the 

 radical bundles we have a simple coalescence of two bundles originally 

 distinct. 



In all Polypodiaceae the adventitious roots spring from the cauline 

 network, and not from the base of a foliar bundle, even in those species 

 where, in the adult state, coalescence frequently occurs. 



Monograph of Isoetese.* — L. Motelay and Vendryes publish a 

 monograph of the existing species of Tsoeteaa, founded on the mate- 

 rials left by Durieu. 



Systematic Position of Lepidodendron, Sigillaria, and Stig- 

 maria t — B. Renault maintains his previous view as to the relation- 

 ships of these fossil organisms, against the objections of Williamson 

 and Hartog. He considers that those Sigillarife which can be deter- 

 mined with certainty belong to the Gymnosperm type, while the 

 species of Lepidophlois have the characteristics of Lycopodiacese. 

 The Stigrnariai must bo regarded partly as rhizomes of Gymnosperms ; 

 the anterior portions must have had only leaves with monocentric 

 vascular bundles, the anterior part, after the fall of the leaves, only 

 adventitious roots with tricentric vascular bundles ; while in the 

 middle were both roots and leaves. This may serve to explain the 

 conflicting descriptions of various writers. 



• Actea Soc. Liiin. Bordeaux, xxxvi. (1883) (10 pis.)- Sec Flora, Ixvii. 

 (1884) p. 47. 



t Renault, B., ' Considerations sur les rapports des L^pidodendrons, des 

 Sigillaires et des Stigmarias,' 32 pp. (1 pi.) 1883. See Bot. Ztg., xlii. (1884) 

 p. 139. • 



