ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 739 



describes his own investigations to determine the presence or absence 

 of mesarch development in Lycopodium. The general conclusions to 

 which he has come are that the position of the protoxylem in the 

 primary wood-bundle of vascular cryptogams is very variable, and may 

 be almost anywhere in the strand. It is therefore of little value in de- 

 termining the relationship of one group to another. A constant primitive 

 feature, however, of vascular cryptogams is the presence in the stem of 

 cryptogamic wood — centripetal xylem continuous with the protoxylem 

 elements. Whenever such a feature occurs in any of the higher plants 

 it is evidence of affinity with the vascular cryptogams in general, and 

 not with any particular group of them. 



Spore-wall of Equisetum.* — R. Beer gives an account of the de- 

 velopment of the spores of Equisetum. The wall of the mature spore 

 consists of four layers, viz. the outside layer (the elater), the " middle 

 layer," the exospore, and the endospore (innermost and last-formed). As 

 to' the origin and interpretation of these four layers, there is a surprising 

 diversity of opinion. The author summarises the views that have been 

 expressed : — 1. All four layers are formed by the spore-protoplast in 

 centripetal succession. 2. The outermost and the middle layer are de- 

 rived from the special-mother-cell wall, the exospore and endospore 

 from the spore-protoplast. 3. The outermost layer is derived from the 

 special-mother-cell wall ; the middle layer, the exospore, and the endo- 

 spore are formed by the spore-protoplast. 4. The outermost layer is 

 formed by the tapetal cytoplasm ; the middle layer, the exospore, and 

 the endospore are formed by the spore-protoplast. The author has care- 

 fully studied the spore-development in E. arvense and E. limosum, and 

 describes the nuclear changes and the formation of the spore-wall. The 

 first wall formed becomes subsequently the exospore, and with the endo- 

 spore is the product of the spore-protoplast ; while the middle layer and 

 the elater-layer are successively formed by the tapetal cytoplasm. 



Fossil Cone of Calamostachys Binneyana.f — H. H. Thomas de- 

 scribes a cone of Calamostachys Binneyana (Carr.) attached to a leafy 

 shoot. It was found in the Lower Coal Measures at Huddersfield. The 

 leaves are small, linear, and arranged in whorls, but not fused at base. 

 They are almost identical in structure with the bracts. Between the 

 whorls of leaves a large number of small, black, hair-like structures occur 

 on the stem. At the base of the cone is a ring of tissue much like the 

 annulus of a modern Equisetum cone. The cone described is probably 

 identical with the impressions known as Paracalamostachys Williamsoni 

 Weiss and with C alamo star lnjs grandis Zeiller, which has similar leaves ; 

 but it is possible that the name Calamostachys Binneyana represents a 

 type rather than a species. The bracts of the cone cannot be regarded 

 as sterilised sporophyll lobes. 



Mesostrobus, a new Fossil Cone.} — D. M. S. Watson describes 

 Mesostrobus, a new genus of Lycopodiaceous cones from the Lower Coal 



* New Phytologist, viii. (1909) pp. 261-6. 



t Tom. cit., pp. 249-60 ( 1 pi. and- figs.). 



% Ann. of Bot., xxiii. (1909) pp. 379-97 (1 pi.). 



