Oct. 14, 191 8 Hardening Process in Plants 87 



calcium malophosphate. Evidence of the identity of this substance 

 is given by the spherocrystalUne form {46) ; its reaction with ammonium 

 molybdate and magnesia mixture, showing the presence of phosphates; 

 replacement of the spherocrystals by gypsum crystals on treatment with 

 dilute sulphuric acid; carbonization on treatment with concentrated 

 sulphuric acid; slow solubility in water; solubility in saturated solu- 

 tions of dicalcium and tricalcium phosphate and insolubility in saturated 

 monocalcium phosphate. Crystals of maleic acid were obtained by 

 microsublimation from cabbage leaf. After fixing in Carney's solution 

 these crystal patches are to be found in great abundance in the older 

 leaves, which are not frozen as easily as the leaves up to an inch in 

 length. The crystals are more abundant in hardened than in nonhardened 

 cabbage leaves of the same size. Precipitation of the malophosphate 

 in the injected areas seems to be caused by greater concentration there, 

 owing to some effect of the freezing. Since Carnoy's solution kills the 

 tissues very rapidly, it is not probable that a diffusion from the sur- 

 rounding tissue into these spots would occur to any great extent. 



GROWTH DEVELOPMENT IN THE INJECTED AREAS 



On standing at room temperature for a few minutes the injected areas 

 of cabbage often disappear, and no trace of them can be seen for two 

 or three days after freezing. At about the third day the spots again 

 become evident as slightly raised areas sharply defined. The raised 

 portions are a little lighter in color than the rest of the leaf. A decrease 

 in the number of chloroplasts in these areas gives the leaf a mottled 

 appearance. Similar conditions have been observed by Ritzema Bos 

 {41) on other plants of this genus (Brassica napus) as a result of frost 

 injury. The young intumescences grow very rapidly for 10 days or 

 more and may reach a relatively enormous size, showing in section 

 a thickness many times that of the normal leaf. They are often of 

 a circular shape, but they may have any shape, corresponding to the 

 coalescence of the injected areas as they increase in size (PI. 9). When 

 a large portion of the tissue is injected, it is difficult to keep the entire 

 leaf from dying, but death may be prevented by placing the plant in a 

 saturated atmosphere. The entire leaf may be a mass of intumescences 

 so that it is rolled and thickened in all manner of shapes. The swell- 

 ings occur along the veins of the leaf more abundantly than over the 

 remainder of the leaf surface (PI. 9, B), although the portions about 

 the veins seem no more liable to injection than other parts. 



In section the tumors when about 4 days old are seen to consist of 

 enormous cells with large nuclei (Pi. 8, C). These large cells are often 

 bi- or tri-nucleate, a condition commonly observed in pathological condi- 

 tions. The walls of these cells are quite thin, and large vacuoles appear 

 in the protoplast. The peculiar large cells recall the pathological 



