434 ' BOTANICAL GAZETTE [November 



between increase of respiration and his postulated stimulus. I have recently 

 shown that there is a difference in the demand for oxygen by the embryos of 

 the dimorphic seeds of Xanthiutn, and that the embryos do not germinate 

 unless the minimum oxygen need is supplied. It cannot be doubted in the 

 case of Xanthium that the oxygen is respired, and that up to the point where 

 oxygen ceases to be a limiting factor, respiration increases with increased 

 oxygen supply. If the seed coat structures limit oxygen sufficiently, the same 

 conditions would obtain in any germination where free oxygen is necessary. 

 Becker's contention, therefore, seems to be without sufficient foundation, 

 especially since he made no attempt to measure the intensity of respiration 

 under the conditions of his experiments. The idea that oxygen is a stimulus 

 which " releases the mechanism" of germination is a conception typical of the 

 German school of stimulus physiologists. Becker is therefore orthodox in 

 his interpretation of the less obvious chemical and physical changes in the 

 germination of seeds. The Germans seem to find it difficult to grasp Black- 

 man's conception of limiting factors, and apply it to the problems of plant 

 physiology; or perhaps they merely prefer to leave the ultimate chemical 

 phenomena of life and growth veiled under the term stimulus, which admirably 

 conceals our ignorance of the real processes. 



A study of the physical characters of the inclosing structures of the Com- 

 positae should disclose the causes of the irregular behavior Becker reports, 

 and careful exact studies of the chemical processes in the germinating seeds 

 will show in how far the embryos are responsible for any of the noted differ- 

 ences. — Charles A. Shull. 



Cecidology.— Among the recent important European publications are 

 the following: A paper by Rubsaamen 1 * on the cecidia of Africa and Asia 

 describes and figures 38 cecidia from Africa and 6 from Asia. These are 

 grouped with reference to the host plants and assigned to genera only. Most 

 of the figures are for the purpose of showing the gross anatomical characters 

 of the galls, 



A paper by Pantanelli 1 * on the Acarus cecidia of the vine describes both 

 the hypertrophies and the parasites. It is well illustrated with photographs 

 of the injuries, microphotographs showing structures of the cecidia, and line 

 drawings of the parasites. The subject is treated primarily from the stand- 

 point of plant pathology and includes a description of one new species {Phyl- 

 locontes viticolus) and an excellent bibliography. 



A paper by Paris and Trotter 1 * gives a very important chemical study 

 of the well known European gall of Neuroterus baccarum and the unaffected 



saamen 



ioa-13 



V. Gallen aus Africa und Asien. Marcellia 10 



J 4 Pantanelli, E., L'Acariosi della vite. Marcellia Io;x33"iS°- I 9 11 - 



** Paris, G., and Trotter, A., Sui composti azotati nelle galle di Neuroterus 



baccarum. Marcellia 10:150-159. 1911. 



