Allgemeines. — Anatomie. 147 



reVelent ä Pevidence une propri^te' qui jusqu'ici n'a jamais ete 

 attribuee qu'aux etres vivants: I'irritabilite\ 



Quelques experiences sur l'hydroquinone et la laccase 

 terminent cet important memoire dont la conclusion generale 

 peut etre formulee de la maniere suivante: 



Quel que soit le phenomene organique que Ton examine, 

 les manifestations electriques apparaissent intimement liees aux 

 reactions chimiques; meme lorsque Celles ci sont quantitativement 

 si faibles que rien ne les revele encore ä notre Observation, la 

 rupture de l'equilibre moleculaire est annoncee par le 

 degagement de force electromotriee et lorsqu'un catalysant 

 comme le laccase accelere les reactions chimiques, les mani- 

 festations electriques sont toujours paralleles ä celles-ci. 



A. Giard. 



Jeffrey, E. C, The Structure and Developement o f 

 the Stern in the Pteridophyta and Gymnosperms. 

 (Philosophical Transactions of the Royal Society of London. 

 Series B. Vol. 190. 1902. p. 119.) 



The author describes the anatomy of the young plant of 

 Danaea alata and simplicifolia, also of other Marattiaceae , 

 shewing that in this order the vascular System may be traced 

 back to a Single tubulär stele interrupted by foliar lacunae. In 

 the more complex mature condition the primitive stelar tube is 

 represented by the outermost ring of steles, while those lying 

 within are of later origin and are derived from its inner wall. 

 It is shewn also that the vascular system of all the other Fili- 

 cales, where it is not protostelic, is to be derived from a similar 

 tubulär stele. 



In Osmunda cinnamomea the author has discovered the 

 existence of an internal endodermis and also, in the neighbour- 

 hood of the branches, of an internal phloem : which tissues 

 become continuous with the external endodermis and phloem 

 through the ramular gaps. From these and other facts he 

 decides that the vascular system of the whole order should be 

 regarded as arising by reduction and specialization from a 

 typically polystelic ancestral type. It is also held possible that 

 the central cylinder of Schizaea may be derived by reduction 

 from a polystelic predecessor. 



In Pteris aquilina, Davallla fijlensis and the Cyatheaceac 

 the external ring of steles represents the primitive stelar tube, 

 from which the meduilary Strands are to be derived, as were 

 those of the Marattiaceae. In Anthrophyum semicostatum and 

 reticulatum it appears that the internal phloem is not continuous 

 on the under surface of the stelar-tube, and it is stated that 

 this feature is quite common among the Polypodiaceae. In 

 Anthrophyum reticulatum and plantagineum no internal endo- 

 dermis is to be found. Vittaria elongata has no internal phloem, 

 and again in Davallia stricta the centre of the tubulär central 

 cylinder is occupied by a parenchymatous pith ; although no 



10* 



