258 Anatomie. — Biologie. 



Baker. R. T., The Australian Grey Mangrove. (Journ. and 

 Proc. Roy. Soc. New South Wales. IL. 3. p. 257—281. PI. XXVII— 

 XLVI. 1916.) 



The author gives a general account of the Australian Grey 

 Mangrove Avicennia officinalis dealing with the synonomy, systema- 

 tic Position and especially with the anatomy of the wood. He shows 

 (a) that there are practically no true medullary rays, as obtain in 

 the secondary wood of dicotyledons, (b) bands of vertical walls of 

 sclerenchymatous cells of the round or polygonal or short variety 

 limit the length of the rays, (c) that the phloem cells in regulär 

 Clusters on the outer edge of each ring, appear to perform the 

 function of ordinary exterior bark, (d) a remarkable disposition of 

 the wood fibres (e) the work of the cambium is performed appa- 

 rently by the wood parenchyma between the wood fibres and the 

 stone cells (f) that there is nothing in the wood which corresponds 

 with the spring and autumn growths of other dicotyledonous trees. 



It has been frequently stated that the bark of this tree is used 

 for tanning, but the author points out that this does not apply to 

 the Australian species for the bark of both young and fully matu- 

 red trees is very thin and scanty in quantity, while the tannin it 

 contains does not amount to more than 7%. This one fact seems to 

 prove, in the author's opinion, that we have here a distinct, and 

 very probably an unnamed species. A unique characteristic of this 

 tree is that it is impossible to kill it by ringbarking. 



The concentric rings of this tree are peculiar and have given 

 rise to a good deal of discussion, one theory being that they are 

 monthly and probably due to the different conditions of nutrition 

 caused by spring and leap tides. But it is shown that though tro- 

 pical temperatures may cause such rapid growth, such a rate does 

 not hold for the New South Wales plants, — in fact a very slow 

 rate of growth obtains in Australia. Nor do forest fires play the 

 part some writers have assigned to them in connection with these 

 rings, as bush fires seldom occur among the trees. Finally the 

 author puts forward what he considers the most feasible, though 

 not definite, explanation of this remarkable structure (1) the attain- 

 ing of a maximum amount of strength with a minimum amount of 

 weight (2) strength to resist river currents and tides. The trees 

 carry an enormous foliage and are offen found overhanging the 

 water at an angle that would be dangerous to the life of an ordi- 

 nary tree, — hence the necessity for great strength. (3) The collec- 

 tive structure of each ring ensures a great vitality to the tree, for 

 whatever accident may happen to a part of them there is always 

 sufticient tissue to carry on the vital processes. Further, the author 

 believes that each individual „ring" represents a year in the life 

 of a tree. E. M. Cotton. 



Baumgärtel, O., Studien über Pneumatokarpien. (Sitzungs- 



ber. ksl. Akad. Wiss. Wien, math.-naturw. Kl. 1. CXXVI. p. 13-39. 



1917.) 



Pneumatokarpien oder „BlähfrUchte" sind jene Fruchttypen, 



deren Grösse und Form durch den Druck der inneren Atmosphäre 



modifiziert wird. Hiezu gehören die Früchte von Astragahis cicer L., 



Colutea halepica Lam., Col. orientalis Mill., Nigella damascena, 



Staphylea Cumalda DC., St. pinnata. Woher stammt die innere 



Atmosphäre in diesen Früchten? Der Reichtum an CO2 lässt das 



