ISOETES JAPOOTCA, A. BE. 



371 



1 



The primary and secondary tissues of the rhizophore are essentially similar to the 



corresponding tissues of the stem. 



Leaf. — The protoxylem of the collateral vascular bundle is exarch in the lamina, but 



becomes mesarch in the sporangial region of the leaf. 



True sieve-tubes occur in the phloem of the leaf. The ligule is very well developed in 

 Isoetes japonica. It has a protective function; the young ligule envelops the younger 



leaves and also secretes mucilage. 



Systematic— Tl\iQ species of Isoetes can be grouped together under two sections, 



Eu-Isoetes and Cephaloceraton. 



Isoetes occupies an isolated position amongst recent Vascular Cryptogams, and is 

 regarded as the sole living representative of the Class Isoctales. 



In conclusion, we wish to express our thanks to Professor J. B. Earmer, F.R.S., for 

 his vjlluable advice and kindly criticism throughout the course of this investigation. 



POSTSCIIIPT. 



Since the foregoing was written, the first two of a series of articles by Prof. Lang, 

 dealing with the organization of the " stock " of Isoetes laciistris, have appeared * 



Although our interpretation of the general morphology of this plant agrees on the 

 whole with that of Prof. Lang, still, his account of the development of the stelar 

 tissues of the stem from the apical meristem cannot be reconciled with our observations. 



We also differ from him in our interpretation of the mode of growth of the roots from 



the rhizoph 



we consider that there is an actual penetration of the 



•tex of the rhizophore by the developing roots. 



Mso, our conclusions as to the affinities of Isoetes differ from those of Prof. Lang 



.0 claims that this genus represents the last stage of reduction of the Lepidodendron 



*yp 



Bibliography. 



1. Baker, J. G.— Handbook of tlie Fern Allies. London, 1887. 



2. BowEK, F. 0.— Origin of a Laud Flora. London, 1908. 



3- Bbaun, a.— Weitere Bemerkungen uber Isoetes. Flora, xxx. 1847. 



4 



Ueber eine neue Art der Gattuug Isoetes. Monatsb 



1861. 



5 



^vv.i deutsche Isoetes-Axien nebst Wir.ken zur Auf.uchung dcrseibcn (uud ein Anhaug uber 

 einige anslandische Arten derselben Gattung). Vcrhandl. d. hot. Vereiu. d. Prov. Brandenb. 

 und die angrenzend. Land, Heft, iii., iv. Berlin, 1862; 299-333. ,.,.,, 



6. . . Bemerkungen uber die Isoetes-Xrt^n der Insel Sardinian. Monatsb. der konigl. Akad. 



d. Wiss. zu Berlin, 1863. 



7 



H.— Ueber Aulage und Wachstlmm der Wurzehi von Lycopodium uud hoeies. 



Naturwiss. viii. 1874. 



8. Untersuchungen iiber Selaginella spinulosa, A. Br. Gotha, 1897. 



Lang, W. H., " Studies in the Morphology of ImUs:' Part 1, Mem. Proc. ilanchestcr Lit. Phil. Soc. lix 

 ^0. 3, Fe\. 1915 ; Part 2, I. c. No. 8, May 1915. 



