Vegetable Physiology for the Year 183b*. 389 



cuticulay and is only separated from this by the destruction of the 

 organic parts. Besides this siliceous envelope Morren supposes 

 the existence of two other distinct membranes, which form the 

 cuticle of the Closteria? and inclose the green substance ; he 

 however remarks that they only become evident upon the me- 

 tamorphosis of the plant. I consider the inner pellicle to be the 

 analogue of the inner envelope which is formed in the members 

 of Confervae when their spores are ripened, or they begin 

 to increase in any other manner, as tor instance by excre- 

 scence and separation. Morren thinks it possible to explain 

 the motion of the Closterice by the action of opposite electri- 

 cities. The author also gives a very complete description, 

 accompanied with drawings, of the very manifold forms which 

 the Closterice exhibit at different periods ; and by this he shows 

 how at least six of the new species of the genus Closterium, de- 

 scribed by Ehrenberg, belong to one and the same species. 



De Brebisson* also made observations on the enigmatical 

 Diatomece in order to decide the question whether they should 

 be classed with animals or vegetables. On burning a great 

 number of Fragilaria pectinalis an animal smell was noticed. 

 Such a smell would however be a very indefinite character, 

 for various other Algae produce a similar odour on their being 

 burnt to a coal. After the burning of the Fragilaria pecli- 

 nalis, and various other beings of the same kind, Brebisson 

 found siliceous envelopes surrounding them in a very per- 

 fect state, and precisely similar to those exhibited by[the fossil 

 Diatomea? discovered by C. Fischer in the peat- bog near Franz- 

 ensbad, and which led to those beautiful observations that 

 Ehrenberg made known on this subject in the course of last 

 yearf. The results of those latter observations belong pro- 

 perly to geognosy ; but we must add this one remark, that 

 under the fossil Infusoria hitherto discovered, only those beings 

 are to be understood which botanists, as has been previously 

 shown, receive as plants. The occurrence in a fossil state of 

 these minute microscopical plants is caused by the hard sili- 

 ceous envelope, which resists all destroying influences. Kiit- 

 zing's discovery that the envelope of the Bacillaricc consists 

 oi silica, which was mentioned in our first year's report, has 

 by this circumstance been rendered more important. If we 

 observe the same minute plants in the living state, it often 

 happens that amongst them some dead ones occur, which ex- 



* Observations sur les Diatomees. — V Institut de 1836, p. 378. — Ann. des 

 Scienc. Nat. 1836, ii. p. 248. 



f Vide On Fossil Infusoria, Wiegmann's Jrchiv, 1836, p. 333. A trans- 

 lation of Ehrenberg's two papers on this subject is given entire, and with 

 engravings, in the Scientific Memoirs, vol. i. p. 400. — W. F. 



