122 



CHARLES S. RIDGWAY 



Mangin* and others in the membranes of various pollen grinas 

 and pollen tubes and in many fungi, notably in the mj^celium of 

 members of the Peronosporaceae. Mangin has also shown the pres- 

 sence of this substance in phanerogams in various cell walls which 

 are encrusted with carbonate of hme^ and also in the achenes 

 of Lithospermum, Cynoglossum, etc., where it occurs without 

 the deposit of lime. In this last instance its presence is claimed 

 by him to be related to the disappearance of the cell contents 

 and with the gradual destruction of the parenchyma. The same 

 author has also seen it in the walls of cells bordering tissues which 

 have become suberized in consequence of injuries. Strasburger 

 and Hillhouse^" mention the presence of "callose mucilage 



in old tissues and membranes which are distinguished by 

 rapid solution, e.g., the callose of sieve tubes, the sporangium 

 wall of pollen mother cells." In the peculiar root-hairs herein 

 described, however, no deposits of calcium carbonate were found, 

 the cell contents had not disappeared, the adjacent parenchyma 

 cells were apparently not breaking down, and no evidence of 

 injury of the hairs could be detected; nor are root-hairs structures 

 which are characterized by rapid solution. 



Both fungi and bacteria have been found closely associated 

 with the root-hairs of some of the plants examined, but so far the 

 writer has been unable to show that they are in any way respon- 

 sible for this unusual occurrence of callose since they were as fre- 

 quently found in and around thin-walled hairs as with callosed 

 ones. No conclusive evidence has been found, as yet, which 

 throws sufficient light on the physiological significance of cal- 

 losed root-hairs to warrant conclusions. It is believed, however, 

 that the phenomenon has its causative agent in certain soil condi- 

 tions as yet undertermined, and experiments along this line are 

 now in progress. 



'Mangin, L., loc. cit. 



' Mangin, L., Sur la constitution des cystoliths et des membranes incrustces de 

 carbonat de chaux. Compt. Rend. 115 : 260. 1S92. 

 "> Strasburger, E. and Hillhouse, W., loc. cit. p. 429. 



