NOTICES OF BOOKS. 89 



pollen, wliereas on the north side of the same catkin the filaments were 

 only about 3 millimeters long and the anthers still close. 



The first article by Dr. Cohn himself is on the function of 

 the bladders of Aldrovanda and Utricular ia. This was presumably 

 written before Mr. Darwin's observations on Droser-a wei-e published, 

 and also before Dr. Hooker's paper on " Insectivorous Plants" was 

 known in Germany, as the author speaks of the one as unpublished 

 and does not mention the other. Dr. Burdon Sanderson's paper on 

 Bioncea he alludes to, and his investigations were undertaken with the 

 view of ascertaining ^whether these plants really draw nourishment 

 from the insects and other animals captured. The leaves of Aldro- 

 vanda possess a certain amount of irritability, or the power of closing 

 over captured animals. A marvellous variety of insects and small 

 water animals was found in the closed leaves, such as minute Crus- 

 tacea, larvae of Diptera and Neuroptera, various genera of the Radiata, 

 and living Algce of the Diatomacece, Confervacem, Nostocacece, etc. 

 From the absence of vascular bundles in the glandular hairs of Aldro- 

 vanda, it is assumed that the seat of the phenomena of irritability aud 

 contractibility is in the parenchyma, and not in the fibro-vascular 

 bundles. And there is no doubt whatever that this peculiar leaf- 

 structure is intended for the capture and killing of animals. With 

 regard to the question whether plants like Aldrovanda digest and 

 absorb the soft parts of the creatures entrapped. Dr. Cohn seems in- 

 clined to admit the possibility of such being the case. Indeed, he 

 argues that the total absence of roots from Aldrovanda would seem to 

 favour this opinion. The same observations apply to Utricularia vul- 

 garis. Dr. Cohn also puts it in this way : why should plants possess 

 traps evidently designed for catching insects, if those insects are of no 

 use to them after they are caught ? 



Dr. Cohn also contributes articles on the development of the genus 

 Volvox (illustrated), and a continuation of his researches on Bacteria, 

 also illustrated. This paper treats more particularly of the 

 systematic arrangement of the Bacteriaceous genera. Cohn, it should 

 be remembered, regards this group as belonging to the Algai rather 

 than the Fungi, and as scarcely separable as a family from the Phyco- 

 chromacecB. He formerly suggested the name of Schizosporece instead 

 of Schizomycetes for this group, and this he now proposes to alter to 

 the more appropriate designation of SchizophytcB. He concludes with 

 a synopsis of the genera. 



Dr. Eidam is the author of another paper on the Bacteria. He 

 confines himself to the efi'ects of temperature on B. Termo. His 

 experiments revealed the following principal facts. At and below 

 + 5° C. this species is benumbed with cold, and at half a degree higher 

 it begins to increase, but in this condition it proceeds very slowly. A 

 temperature of 30° to 35° C. is the most favourable to its rapid pro- 

 pagation. Exposed to a continuous temperature of 40° C, it loses the 

 power of growing, and falls into a state of torpor, from which it rouses 

 again upon the return of favourable conditions. Exposure to 50° C. 

 for three hours continuously is sufiicient to kill this species, when it 

 is dispersed in a watery fluid. In return, it possesses great powers of 

 resistance to heat and cold in a dry state, and will long retain its 

 vitality. 



