ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 401 



through several nodes. As the leaf increases in eflRciency the leaf -traces 

 increase in number. Advanced types of dicotyledons show a progres- 

 sive disappearance in cambial activity in the leaf -traces, although these 

 are often of greater size than the bundles of the stem. The greater 

 number and importance of the leaf -traces, together with the relatively 

 greater importance of the secondary axes of higher types, result in a 

 crowding of strands at the nodes and a more scattered distribution of 

 the stem bundles, while at the same time amphivasal strands are formed. 

 Physiological advantage probably explains the disappearance of secondary 

 growth in leaf-traces ; this disappearance may extend also to the bundles 

 in the stem and results in a practically monocotyledonous structure. 



S. G. 



Leaf-structure in Nilssonia. — E. Florin {Tom. cit., 1-10, 1 pi., 

 1 fig.). A study of the leaf-structure of Nilssonia polymorpha, with 

 special reference to its systematic position, confirms the results obtained 

 by Nathorst, Thomas and Bancroft as to the sunken stomata with 

 round, unthickened guard-cells, and the general structure of the cuticle. 

 The author supports their view that this genus differs in these points 

 from the more complex Bennettitales, but appears to be closely related 

 to recent Cycads. S. G. 



CRYPTOGAMS. 



Pteridophyta. 



Homosporous American Lepidostrobus.— John M. Coulter and 

 W. J. G. Land {BoL Gaz., 1921, 72, 106-8). Though the coalfields 

 of Europe have yielded perfectly preserved strobili of Lepidodendron, 

 showing heterospory, the coalfields of America have, with but two 

 exceptions, yielded nothing but casts. A fragment of a strobilus from 

 Iowa was cut and described by Coulton and Land in 1011 {Bot. Gaz. 

 1911, 51, 449-53). Further fragments of the same cone have since 

 been found, showing the strobilus to have been 22 cm. long and 5 cm. 

 wide. It is well preserved, but the sporangia are nearly all completely 

 empty. The few spores found average 27 /x in diameter. The evidence 

 is strong that this strobilus was homosporous, which is a matter worthy 

 of record and of consideration, since it simplifies the question of the 

 origin of the modern Lycopodiales, a homosporous group. A. Gepp. 



Fourth Contribution to our Knowledg-e of the Anatomy of the 

 Cone and Fertile Stem of Equisetum. — Isabel M. P. Browne 

 {Annals of Botany, 1921, 35, 427-56, 1 plate, 12 figs.). A study of 

 the cones of Equisetmn stjlvaticum, E. debile and E. variegatum. The 

 results are as follows : (1) The vascular system of the cone of E. 

 sylvatmmi resembles that of E. maximum, but on a smaller scale, and 

 better developed. (2) That of the cone of E. dehih is much reduced 

 and forms a loose network ; and frequently many parenchymatous 

 meshes, originating below the cone, persist far into the cone, some even 

 traversing the whole cone. (8) The stele of the cone of E. variegatum 

 is also of reduced type. (4) On grounds of comparative anatomy the 

 separation of protoxylem and metaxylem in the internodes of the cones 



