4 ON NAIAS GKAMINEA DEL., VAH. DELILEI MAGNUS. 



the varietal name of Delilei, on account of a structural peculiarity 

 which will appear further on. 



II. — The Genus and its Divisions. 



The genus gives its name to the natural order Naiadacem, which 

 is allied to the Potamogetonaaea, but systematists are by no means 

 agreed as to the respective limits of either family. Willdenow 

 separated the group to which N. graminea belongs from Naias 

 proper, under the generic name of Caulinia* on account of the 

 male flowers not having the quadrifid perianth of Naias proper; 

 but Eobert Brown reunited the two groups of Naias and Caulinia 

 into Naias Linn. There is no doubt, however, that each of these 

 divisions forms a very natural group sharply separated from the 

 other by well-marked characters drawn from the leaf, stem, and 

 fruit. All these points have been carefully worked out by Dr. P. 

 Magnus in a work which he modestly entitled 'Beitrage zur 

 Kenntniss der Gattung Najas, L.' (Berlin, 1870); and no one can 

 investigate the morphology and anatomy of a plant of this genus 

 without admiring the minute and conscientious investigations of 

 this author. In preparing the following notes I have referred 

 again and again to this memoir, and I cannot speak too highly of 

 the help derived from it. 



Dr. Magnus gives the following diagnoses of the two subdivisions 

 of the genus, to.: — 



" § Eunajas Asch.-— Spine-teeth chiefly on the stem and backs 

 of the leaves. Flowers dioecious (? in all). Anther four-chambered 

 (? always). Seed-shell consisting of a many-layered stony paren- 

 chyma. Conducting bundles of the stem divided from the inter- 

 cellular spaces by two to three layers of parenchyma-cells. Leaf 

 furnished with a small-celled epiderm, which rises very sharply 

 from the large parenchyma-cells of the leaf. 



" § Caulinia Willd. — • Spine-teeth absent from the stem and 

 backs of leaves. Flowers in most species monoecious (? in all). 

 Anther one- to four-chambered. Seed-shell formed of three layers 

 of cellular tissue. Conducting bundles of the stem divided from 

 the intercellular spaces by a layer of parenchyma-cells ; leaf without 

 the small-celled epiderm." — 'Beitrage,' pp. 55, 56. 



The plant which forms the subject of this notice belongs to the 

 section Caulinia, and its synonymy^and principal book-references 

 are the following : — 



III. — Synonymy op the Plant. 



Najas graminea Delile, Flore de l'Egypte. M&noire sur les plantes 

 qui croissent spontanement en Egypte; par Alire Eaffeneau 

 Delile, p. 1. Florae iEgyptiacse illustratio No. 874, p. 75. 

 Explication des planches, p. 282, pi. 50, fig. 8. 

 Chamisso, Aquaticse qusedam diversee affinitatis. Linnsea, vol. 

 iv., 1829, pp. 502-3. 



* ' Memoires de l'Academie Royale des Sciences de Berlin, 1798, classe de 

 Philosophie Experimentale,' page 87. 



