iqi2] CURRENT LITERATURE 555 



I 



-soils in which Azotobacter chroococcum is extremely active in fixing nitrogen. 

 By the use of cultures, which are described, 21 species of soil algae were found, 

 all but two being Cyanophyceae, and the best represented family being 

 Nostocaceae. It is concluded that these algae are an important source of 

 energy for Azotobacter. — J. M. C. 



Podozamites distans.— The fragments referred to this form, sometimes 

 under the name of Cycadocarpidium, have been regarded by some as pinnate 

 leaves, and by others as shoots with spirally arranged leaves. The mega- 

 sporophylls, with two ovules at the base, bearing some resemblance to those 

 of Dioon. are collected into a loose cone. Nevertheless, Schuster 34 comes to 

 the conclusion that Podozamites distans is a primitive conifer, coming from the 

 same Cycadofilicales stock which gave rise to the Ginkgoales. Consequently, 

 he would have Podozamites removed from the Cycadales and placed with 

 Coniferales. Schuster's figures, as well as two of Nathorst's which he 

 reproduces, seem to the reviewer to favor relationship to the Cycadales. — 

 Charles J. Chamberlain. 





Anatomy of Equisetum. — Lady Isabel Browne 35 has investigated the 

 anatomy of the strobilus and of the fertile stem of Equisetum. The xylem 

 situation in this genus is of great interest, and in the axis of the strobilus it is 

 best developed. At the nodes, the xylem forms a ring or occurs as bands of 

 varying width; while in the internodes the xylem breaks up into definite 

 strands. E. arvense, E. palustre, and E. limosum form a series showing pro- 

 gressive reduction of the xylem. The study of the strobilus further confirms 

 the view that the "sporangiophores" are not lobes of a suppressed foliar 

 member, but are "whole appendages/' which would seem to indicate that they 

 are not sporangiophores. — J. M. C 



Stomata of Bennettites. — Lignier 36 has discovered the existence of 

 stomata on the interseminal scales of Bennettites MorierL The structure as 

 figured is obvious enough, and about the guard cells there are concentric 

 subsidiary cells. Lignier raises the question whether the presence of these 

 stomata does not indicate freedom for the movement of air among scales 

 and ovules, and therefore less compactness of structure than develops later, 

 when the seeds mature and the tips of the interseminal scales hypertrophy. 

 Since stomata occur within the ovaries of angiosperms, as Lilium for example, 

 their presence does not prove the free circulation of air. — J. M. C. 



3 < Schuster, Julius, Bermerkungen iiber Podozamites. Ber. Deutsch. BoU 



Gesells. 29:450-456. pi. 17. 191 1. 



NE 



P., Contributions to our knowledge of the anatomy of 

 of Equisetum. Ann. Botany 26:663-703. pis. 64, 65. 



figs. 10. 191 2. 



interseminales 



(Sap. et. Mar.), Bull. Soc. Bot. France 59:425-428. Jigs. 2. 1912. 



