ZOOLOGY AND BOTANY, MICEOSCOPY, ETC. 293 



importance as indicating the type of structure from which the vascular 

 systems of the Osmundaceas were derived. A. Gr. 



Anatomy of Equisetum arvense.— A. Maillefee (.4/// Soc. 

 Elvetkd Sci. Nat. Lugano : 6-9 Settembre, 1919, pt. II. Aarau : 1920, 

 p. 110). The bundles of the leaf-sheath have a centripetal xylem placed 

 below a phloem bundle ; the anatomical arrangement in the leaf is the 

 excentric arrangement of Ghauveau (1911). In the stem the leaf-trace 

 is reduced to two vessels placed side by side so that the xylem is formed 

 neither in a centrifugal nor in a centripetal manner ; it should however 

 be regarded as virtually centripetal ; a lacuna is soon formed round these 

 vessels ; the metaxylem is also centripetal : one must not however 

 follow Owyune-Yaughau (1901) in regarding it as the analogue of the 

 cauline centripetal xylem of the Lycopodiaceas : for it is formed after 

 the leaf-traces (protoxylem), and is clearly in relation with the roots 

 formed at the base of the adventive buds, to which it bears the same 

 relation as the xylem of a branch does to itsradicels. One could explain 

 this carious anatomy of the Equ,ketum stem by saying that it is a 

 combination of a stem with an excentric arrangement and a root, or 

 again that the stem contains at the same time a siphonostele and an 

 actinostele : the vascular lacuna represents the xylem of the stem, and 

 the metaxylem the xylem of the root ; the phloem is in common. This 

 combination of the anatomy of a stem with that of a root is due to a 

 physiological cause — the fact that the stem is a rhizophore. A. G. 



Further Notes on the Ecology of Phyllitis hybrida.— V. Vouk 

 {Oest. Jjot. Zeitsclir., 1916, 897-9). A continuation of the discussion 

 between the author and Morton on the subject. The former designated 

 FhylUtis hybrida as a mesophyte with well-developed xerophytic 

 adaptations. Morton describes it as a typical hygrophyte. In the 

 present paper A'ouk meets Morton's complaints of insufficient attention 

 to his argument, discusses the change of ecological conditions caused 

 by the felling of woodland, and maintains that though forest plants are 

 shade plants they are by no means always hygrophytes. Xerophyte 

 and hygrophyte designate ecological extremes, and the same species 

 cannot tolerate both conditions. Since P. hybrida is found in shady 

 damp clefts and hollows in limestone rocks, as well as often in open 

 sunny xerophil localities, Vouk regards it (as stated above) as a meso- 

 phyte with well -developed xerophytic adaptations. By no means is it a 

 hygrophyte. Its xerophytic characters are its compact, rosette-like 

 habit ; coriaceous, thick and ligulate leaves ; firm epiclermis : hairiness 

 (scales) ; the same characters as those of Christ's xerophytic form of 

 Elaphoglossum. The author maintains that the factors " shade " and 

 "damp " must be regarded as absolutely distinct, and proposes to carry 

 out experiments to prove his contention. As regards its ecology, P. 

 hybrida entirely resembles Ceterach officinalis, which is on the -^diole a 

 xerophyte, provided with all xerophytic characters; but at the same 

 time a dweller of clefts and hollows under a somewhat altered appear- 

 ance. Both species are capable of adaptation. Since the cardinal 

 points of light-requirement are very wide for both plants, they may be 



