ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 215 



from a simple protostele which opens out into a siphonoslele. This 

 shows a considerable reduction in the cone by the development of large 

 parenchymatous meshes or longitudinal tracks, and still further reduction 

 in the internodes of vegetative shoots. A. Gepp. 



Third Contribution to our Knowledge of the Anatomy of the 

 Cone and Fertile Stem of Equisetum. — Isabel M. P. Bro^vne {Ann. 

 o/Bot, 1920, 34, 237-63, 2 pis. and figs.). An account of the fertile 

 region in E. hyemale and E. giganteum. 1. The following series shows 

 the species arranged according to the gradual reduction of the vascular 

 system in the cone : {a) E. arvense, (b) E. hyemale, (c) E. pahistre, 

 (d) E. giganteum, (e) E. maximum, (/) E. Umosum. In («), relatively to 

 its size, the vascular system is by far the best developed, and in (e) and 

 (/) by far the most reduced ; in (b) (c) [d) the reduction of xylem has 

 proceeded in somewhat different ways, but on the whole to much the 

 same degree. 2. The reduction of the xylem of the cone is manifested 

 in E. hyemale and E. giganteum, as in the other species studied, by the 

 persistence of parenchymatous meshes, arising vertically above traces 

 that have departed, upwards into more than one internode, and by their 

 extension laterally above traces given off from at or near the edge of 

 a strand. Both phenomena may be considered to be due to poor 

 development of axial xylem at the nodes of the cone. 3. Specially 

 characteristic of E. hyemale, and showing relatively good development 

 of the vascular system, are the following points : \a) the closure of 

 parenchymatous meshes by the formation of additional tracheids at 

 the node rather than by the oblique course of the tracheids of the 

 branches of a strand above the departure of a trace ; {])) the relatively 

 large number of parenchymatous meshes and the high proportion 

 among these of meshes of the first and second orders. 4. In E. gigan- 

 teum a relatively high development of the xylem of the cone is shown : 

 (a) by the slightly greater radial extent of the xylem in this species ; 

 lb) by the not infrequent development of wide internodal tracts of 

 xylem, involving the absence of parenchymatous meshes over median 

 traces ; (c) by the fact that closure of parenchymatous meshes more 

 often involves the formation of additional tracheids than the oblique 

 course, and ultimate fusion of groups of tracheids lying on either side 

 of the mesh ; and {d) by the fact that this fusion of strands, owing to 

 the formation of additional tracheids, not infrequently occurs con- 

 siderably below the node. 5. Both in E. hyemale and E. giganteum 

 the sporangiophores of successive whorls alternate with considerable 

 regularity. But the traces at their insertion on the axial stele do not 

 alternate regularly with those of the whorls above and below. In both 

 species regular superposition occurs when parenchymatous meshes persist 

 unnarrowed on either side of a trace-bearing strand through two or 

 more nodes. This superposition, being due to poor development of 

 axial xylem at the nodes, is less common than in E. maximum or in 

 E. Umosum. Within tiie species the specimens with less well-developed 

 xylem show more numerous examples of superposition of traces. 6. 

 The traces of the sporangiophores of E. giganteum are the most massive 

 yet described for the genus. 7. The traces of the lowest whorls of the 



