24 EXPERIMENT STATION BECOED. ITol. 38 



It was found that the species of spineless cacti having relatively thick integu- 

 ments (this term including the cuticle, epidermis, crystal-bearing layer, and 

 several layers of thick-walled cells lying immediately below) are more re- 

 sistant to cold than those having somewhat thinner integuments. The thick 

 integument was found to protect the cactus plant against sudden and severe 

 temperature changes at any season. The freezing point of the cell sap of the 

 cactus plant was found very little below that of pure water. The collecting 

 and freezing of water in the intercellular spaces of the plants was not in itself 

 particularly harmful to the plant, nor was the protoplasm poisoned by the con- 

 centration of the cell sap resulting from the withdrawal of part of the water 

 from the cells by freezing. A study is reported to show that the protoplasm of 

 these plants can withstand a certain low critical temperature without injury, 

 but a temperature below this vnll destroy them. 



The author found that Opuntia casWlw and O. ellisiana are resistant to 

 lower temperatures than any of the other species studied, being injured at 

 temperatures of —14 and — 16° C. (6.8 and 3.2° F.), but 0. fictis indica and Bur- 

 bank Special are injured by temperatures of — 5 and — 6° 0. These results, 

 which were obtained in the laboratory, agree in general with observations on the 

 same species under field conditions. A temperature which damaged the plants 

 to any extent was found to kill them if continued long enough or if repeated 

 several times. Differences in the character of the protoplasm, due allowance 

 being made for the thickness of the integument when the cold extends over a 

 short period of time, are believed to explain why one species of cactus is more 

 resistant to cold than another. 



Some studies on the germination of the seed of Oryza sativa, I. Nagai 

 (Jour. Col. Agr. Imp. Univ. Tokyo, S (1916), No. S, pp. 109-158, pi. 1, figs. 2).~ 

 Experimental results are reported in an attempt to verify and supply further 

 data on the physiology of germination in the seeds of the Graminea;. The er- 

 periments were conducted with the seed of O. sativa and Zea mays and tne 

 problem studied under the following subject heads: (1) The rSle of the selec- 

 tive-permeable septum of the seed covering in the viability of the seed, (2) the 

 seat of the selective-permeable septum in the seed covering, (3) the role of 

 oxygen in germination, (4) the effect of H and OH ions in germination, and 

 (5) the influence of extremes of temperature on the germinative powers. All 

 experimental data are presented in tabular form and briefly discussed. The 

 general conclusions arrived at by the autnor follow : 



In the seed covering of 0. sativa and Z. mays selective permeability was ob- 

 served. The seat of the selective-permeable septum in Oryza is most probably 

 confined to the cutinized inner wall of the inner integument which lies directly 

 above the aleurone layer in the fully matured grain. 



The germinability of desiccated hulled Oryza was slightly affected by 24 

 hours' steeping in six-normal sulphuric acid, chloroform, acetone, ethyl ether, 

 commercial absolute ethyl alcohol, picric acid (aqueous solution) ; and ethyl 

 alcoholic (commercial absolute) solution of thymol, naphthalene, and «-naph- 

 thol, whereas the air-dried grains were killed by similar treatment. In the 

 same manner the air-dried seed of Zea were killed by five-normal sulphuric 

 acid, hydrochloric acid (21 hours), commercial absolute ethyl alcohol, ethyl 

 alcoholic (commercial absolute) solution of naphthalene, resorcin, a-naphthol, 

 and a-naphthylamine, but not the desiccated grain. The vitality of desiccated 

 hulled grains of Oryza and Zea is lost by 24 hours' steeping in formaldehyde, formic 

 acid, commercial absolute methyl alcohol, methyl ether, acetaldehyde, glacial 

 acetic acid, butyric acid, amyl alcohol, pyridin, aqueous solution of chloral- 

 hydrate, resorcin hydroquinone, and 21 hours' steeping in nitric acid (three- 



