414 SUMMARY OF CURRENT RESEARCHES RELATING TO 



relation to the CyatheoideiS and other ferns, such as Gleichenia, Striithi- 

 opteris, Onoclea, Gysiopteris, Acrophorus, Peranema, Diaealpe, Woodsia, 

 Hi/poderris. In making the comparison, he uses the following criteria : — 



(1) position and branching of the axis ; (2) form and pinnation of leaf ; 

 (:-]) dermal appendages ; (4) characters of the vascular system ; (5) 

 position and constitution of sorus ; (6) sporangia and spores ; (7) 

 protballus and sexual organs. It is pointed out that in these seven 

 respects there is a progressive development in the genera cited above. 

 Thus (1) the dichotomy of Gleichenia becomes rarer in the higher types ; 



(2) the Gleichenia type of leaf is recalled somewbat in Cyatheacese, then 

 lost ; (3) there is a progression from primitive hairs to scales ; (4) the 

 protosiele of Gleichenia becomes by stages solenostelic in Lophosoria, and 

 dictyostelic in all the rest ; also accessory strands appear in Cyatheacese ; 

 (5) the sorus is superficial and not distal ; it shows progress from a 

 simple type in Gleichenia and Lophosoria, to a gradate type in Cya- 

 theacete, Struthiopieris, Onoclea, Woodsia, Cystopteris, and becomes mixed 

 in Hypoderris, Peranema, Diaealpe— -a, condition leading probably to that 

 of Aspidieaj ; (6) the sporangia of Gleichenia are large, few, pleurispored, 

 medially dehiscent ; in Lophosoria, fewer-spored (64) and laterally de- 

 hiscent ; still fewer-spored and obliquely annulate in Cyatheaceae ; finally 

 vertically annulate ; (7) the antheridium tends to become simpler and 

 to produce fewer spermatozoids. Bower considers these ferns to consti- 

 tute a true phylum, the sequence being Gleicheniacege— Cyatheacese 

 (including minor groups such as Woodsiete, etc.) — Aspidiese. 



Sieve-tubes of Pteridium.* — E.M.M. Hume describes the histology 

 of the sieve-tubes of Pteridium aquilinum, with some notes on Marsilia 

 quadrifolia and Lygodium dichotonmm. The distribution of the sieve- 

 tubes around the vascular strand is described, also the delicate proto- 

 plasmic threads traversing the sieve-plates, the formation of the callus 

 and its conversion into slime. No winter callus is formed in Pteridium. 

 Connexions between sieve-tubes and phloem parenchyma cells are frequent, 

 but without any callus. 



Bryophyta. 



(By A. Gepp.) 



Branching in Leafy Hepaticge.t— A. W. Evans gives an account of 

 the modes of branching in the leafy hepaticse. Leitgeb was the first to 

 make a careful study of the subject, and demonstrated inter alia the 

 fact that true dichotomy does not occur in Jnngermanniales, though the 

 apical cell of a future l)ranch often makes its appearance in an exceed- 

 ingly young segment of the main apical cell. Evans calls attention to 

 the two kinds of branching which are found in the Jungermanniacea3 — 

 terminal and intercalary. In the former cases the rudiments arise in 

 very young segments ; in intercalary branching tliey arise in segments 

 more or less mature. 1. Terminal branching includes four distinct types, 

 characterized by the portion of the segment which takes part in branch 

 formation. These types are represented by Frullania, Microlepidozia, 



* Ann. of Bot., xxvi. (1912) pp. 573-87 (2 pis.), 

 t Ann. of Bot., xxvi. (1912) pp. 1-37 (figs.). 



