196 SUMMARY OF CURRENT RESEARCHES RELATING TO 



evidence so far obtained the author inclines to the view that the tubular 

 medullated stele of Platyzoma is the result of upgrade development 

 from within of an original protostele; but the problem cannot be 

 solved until the " sporeling " stages have been investigated, and 

 solenostely and reduction are proved or disproved. A. G. 



New Facts as to the Stelar Theory of Ferns. — J. McLean 

 Thompson {Trans. Roij. Soc. Edinhurgh, 1920, 52, 715-735, 4 pis., 

 9 figs.). The writer has studied the anatomy of various species of 

 the Schizieaceae and Gleicheniace^ with special reference to the -stelar 

 theory. In the SchizEeaceae the author finds that (1) the stelar endo- 

 dermis is an unbroken cylinder without lateral connexions between the 

 cortex and the pith ; (2) the pith is of intrastelar origin, arising by 

 gradual increase of wood-parenchyma and accompanying decrease of 

 central tracheides ; (3) there is no marked increase in diameter of the 

 xylem cylinder or stelar area during transition from solid protostely to 

 the medullated state. In Schizsea dkhotoma the endodermal pockets 

 are intrastelar structures which arise by change of procambial destina- 

 tion within the stele. In the Gleicheniacea ontogenetic progression 

 from protostely to solenostely is seen in GUlchenia pectinata, Loxsoma 

 Cunninghamii and Acrostic/mm aureum, and the evolution of the 

 Lindsaya type can be traced in Lindsaya adiantifolia. Development 

 shows that both the inner phloem and the medulla are of purely 

 intrastelar origin, and there is no evidence of the intrusion of cortical 

 tissues into stele during medullation. Ontogenetic evidence for the 

 ferns appears to show that medullation and the solenostelic and 

 dictyostelic states arise by intrastelar readjustment, in which change of 

 destination is mainly operative. S. Greves. 



Contributions to a Knowledge of the Anatomy and Cell-contents 

 of Ferns. — H. Martin (Dissertation (Gottingen : W. F. Kastner) 

 1916, 137 pp. ; see also Bot. Centralhl., 1918, 138, 154). During 

 microchemical investigation for tannic acid and other substances in 

 seventy-seven representative Filicales, the author paid particular atten- 

 tion to the anatomical structure .of the lesser known species, with the 

 following results : — Acjording to the development and the amount of 

 the thickening of the epidermis of the leaf-.^alk, three groups may 

 be distinguished. Some ferns have a hypodermis. A sclerenchyma- 

 ring is always present, but not a " stiitzscheide." The cells of the 

 main parenchyma are thickened and brown. Idioblasts occur in certain 

 Cyatheacege ; mucilage-canals in the Marattiaceee ; capitate glandular 

 hairs, wbich become less abundant towards the apex of the leaf-stalk 

 {As2Jidii/m Filix-mas). The endodermis entirely surrounds the fibro- 

 vascular bundle of the Osnmudaceae, despite Thomae's statements, as is 

 clearly revealed by Berthold's method of preserving the material. The 

 stele of ferns does not always contain parenchyma in the xylem. 

 Collateral vascular bundles occur in Geratopteris. The protoplasm cells 

 are always collenchymatous. Conducting cells are never present in the 

 phloem, as is easily shown by the method of preservation employed. 

 In Aspidiuni falcatum the sieve-tubes adjoin the tracheides. Theproto- 



