28 EXPERIMENT STATION RECORD. [Vol. 40 



sions derived are believed to throw light on the problem of water absorption by 

 gels and at the same time to give a new view of the complexity of the factors 

 which may operate to determine the rate and direction of growth, as well us 

 absorption and transpiration in the highly complex colloids of the plant. 



Colloidal phenomena in the protoplasm of pollen tubes, 1'. EL LlOTD (Car- 

 negie Inst. Washington Year Book. 16 (1917), ]>i>- 68, 64). — In continuance of 

 reports on previous work (E. S. R., 36, p. 526), the author gives details of studies 

 intended to throw light on the behavior of pollen tubes grown In acids and 

 alkalis in the presence of high concentrations of cane sugar, the results of 

 which are summarized. 



Within the limits of concentration 1/10 to 1/2.560-normal of the reagent, arid 

 or alkali, the maximum swelling rates and maximum total swelling in ari'is 

 occur at 1/10-nornial, malic add, to l '320-normal, hydrochloric acid, and for 

 alkalis at about 1/80-normal. Organic acids cause maximum swelling at higher 

 concentrations than do mineral acids, apparently in direct relation to the degree 

 Of dissociation. At lower concentrations of acids and alkalis, there is a rep: 



sion of swelling rates, especially in hydrochloric acid, this being generally greater 

 for acids, while for alkalis the rates are about equal to or slightly less than for 

 water. 



The author has sought to determine how far parallelism exists between the !„■- 

 havior of protoplasm in pollen and that of gelatin. The effects of a series of 

 acids, hydrochloric, acetic, malic, citric, formic, and oxalic, have been determined 

 for concentrations 1 utx.i to 1 -~>. OH\ normal in association with cane sugar at 16 

 per cent concentration. It was found that no growth occurs at or above 1/3,200- 

 Dormal of the acid. Below that limit growth rate varies Inversely as the con- 

 centration. Kate (also, total) of growth for any concentration varies with the 

 acid. 



There is evidence that pollen tube growth rates are limited by their ability to 



utilize the swelling effects of the acids. The tubes may burst at high concen- 

 trations. 



The parallelism of behavior between gelatin and the protoplasm of pollen 

 tubes, when expressed in terms of accomplished growth, is more apparent in the 

 case of alkalitio than in that of acid media, 



The effect of acids and alkalis on the growth of the protoplasm in pollen 

 tubes. F. B. Lloyd < Hem, Torre* Bo* Clnb, n {1918), pj \ study of 



the pollen of Phaseolua odoratut in hanging drops of various reagents at different 

 concentration-, associated with cane sugar In constant concentration, is said to 

 indicate that the protoplasm of pollen grains is affected DJ adds and alkalis as 

 is gelatin, and that the increased BWelllng cause] b\ the reagents can be utilized 



In growth. This protoplasm is extremely sensitive to low concentrations of both 

 acids and alkalis. 



The construction of a biocolloid exhibiting some of the water relations of 

 living plants, D. T. HacDouqax. {Carnegie Inst. Washington Tear Book, n'< 

 (1911), pp. 59, 60). — It is stated that the systematic endeavor to construct, by 

 methods which are described, a colloidal mixture displaying some of the funda- 

 mental physical properties of protoplasm in plants has resulted in finding that a 

 mixture of substances of two of the three more important croups of constituents. 

 Carbohydrates and proteins, shows the imbibitional behavior of tissues and 

 tracts of protoplasts Of the plant. The differential action of such blOCOlloids in 



solutions yields striking parallels with growth. The general Identity as to con- 

 stitution Of these colloidal mixtures and of cell masses and the similarity of 

 their behavior are thought to make it possible to correlate more close!] the 



pr< "I imbibition, metabolism, and growth, and on the basis of their inter- 



