* t 



ISOETES JAPO^'ICA, A. BE. 



369 



Motelay and Veiidryes, viz. " Aquaticse " and " Terrestres " (25, p. 317). But we are of 

 the opinion that the use of these names is misleading and should therefore he avoided. 



b 



The chief characters of the two sections are as follows : — 



Section 1. Eu-Isoetes, noh. 



Leaves with 4 wide lacunae, the outer wall of which is composed of 2-3-5 layers of 

 cells (including the epidermis) ; sometimes provided with hypodermal fibrous strands, 



normally 6 in number, 4 main (1 abaxial and 3 adaxial) and 2 accessory (lateral). 



Sterile leaves very similar to the sporopbylls. Leaf-bases seldom persist as membranous 

 scales, never forming phyllopodes. 



Species growing either submerged, in shallow water (where they are subject to 

 temporary desiccation), or in damp soil. 



Section 2. Cephalocehaton, Gennari (gen.). 



Leaves with 4 narrow lacunae, the outer wall of which consists of one layer of cells 

 {i. e. the epidermis alone) ; normally provided with only 4 hypodermal fibrous strands 

 (1 abaxial and 3 adaxial). Sterile leaves conspicuously smaller than the sporophylls, 

 eventually giving rise to phyllopodium-like scales. Leaf-bases always form persistent 



phyllopodes. 



Includes species inhabiting damp soil, subject to desiccation during a certain period 



of the year. 



Discussion-. 



The systematic position of Isoetes still remains undecided. This genus has in turn 

 been compared with: L Certain Angiosperms (Hofmeister) ; 2. Eusporangiate Perns 

 (Vines, Parmer, and Campbell, 10); 3. Lycopods (including Lepidodendreae, Sigillariea3, 

 and Fleuromeia) (Wilson Smith, Scott & Hill, Bower, Stokey, and Lang) *. 



The supposed resemblance between Isoetes and the Angiosperms is both fanciful and 

 unscientific, and cannot be accepted as any indication of affinity. 



The Pilicinean affinities of this genus are almost entirely based upon gametophytic 

 characters, the importance of which, however, is too frequently underestimated. 



With regard to the morphology and anatomy of the sporophyte, Isoetes has many 

 characters in common with the Lycopodineae (in the wider sense), but these are not of 

 sufficient importance to justify the view that Isoetes belongs to this group. 



The isolated position of the genus Isoetes amongst recent Vascular Crj-ptogams has 

 also been suggested, a separate Class, the Isoetales, co-ordinate with the Eilicalcs, 

 Lycopodiales, Sphenophyllales, etc., being proposed for its reception (Campbell, 10 a; 



followed by Lotsy, 21). 



The evidence derived from the present anatomical investigation is distinctly favourable 



to this view. 



In the structure of the stem-apex and the development of the primary tissues of 

 the stem, Isoetes differs in many respects from lAjcoj^odium or Selaginella, while the 



In these papers the systematic position of hoete$ is discussed in detail ; recupi 



unnccossary 



3g2 



