226 EXPERIMENT STATION RECORD. [Vol.43 



seriation. In some instances also the cells of the wood parenchyma strands are 

 an-anged In secondary seriation, visible under the lens. 



Mucilage or slime formation in the cacti, E. G. Stewart {Bnl. Torrcy Bot. 

 Club, 46 {1919), No. 5, pp. IBl-lGG. pi. i).— Having studied mainly in this con- 

 nection RhipsaUs rhombea, the author reports that he has found in cacti a 

 transformation in the content of many cells in the growing regions into 

 mucilage, whicli by absorbing water may simulate true growth and may be of 

 importance in conserving and regulating the supply of water for the growing 

 cells. Apparently the cell wall is not involved. The mucilage comes from the 

 protoplasm and the formation begins between the cell wall and the protoplasm. 

 As the mucilage increases the nucleus and cytoplasm give way to it until it 

 completely tills the enlarged cell. 



It is not held that all resins, gums, and mucilages are similarly formed. It is 

 stated that the method of secretion here noted in connection with uuicilage 

 cells of the cacti is much more like that of the gland cells of animals than tlie 

 more familiar method by a resinogenous layer of the cell wall as found in many 

 trichomes. 



Origin and development of the pycnidium, F. E. Kempton {Bot. Gaz., 68 

 {1919), No. Jf, pp. 233-261, pis. 6).— The author states that the origin and de- 

 velopment of pycnidia may fall in either of two main methods, meristogeuous 

 and symphogenous, the latter being the less often found and variable and the 

 former being resolvable into two modes, simple and compound with variatioi s. 

 Acervuli arise in the same manner as do pycnidia. The simple meristogenous 

 development is more often found in the Sphjeropsidales. while the compound 

 meristogenous and symphogenous modes are tlie more usual ones found in tlie 

 Melanconiales and Tuberculariacete. 



The formation of fruiting bodies by Penicillium glaucum in concentrated 

 sugar solutions, N. Bezssonof {Ber. Deut. Bot. Geaell., 36 {191S), No. 4, pp. 

 225-228). — The author states that in sugar solutions at concentrations approach- 

 ing saturation P. glaucum continued to live and develop, giving evidence at 

 high concentrations of a tendency to develop reproductive bodies. 



The resistance of plants to cold, II, E. Pantanelli {Atfi R. Accad. Lincei, 

 5. ser., Rend. CI. Sci. Fis., Mat. e Nat., 21 {WIS), I, No. 4, pp. 1^8-153). —In con- 

 tinuation of a report previously noted (E. S. R., 39, p. 52.5), the author gives an 

 account of work done mainly with sunflower, tomato, and maize sulijected to 

 different temperatures. 



No direct relation was found to exist between resistance to cold and the alimen- 

 tary value of the salts furnished to the plant. Nitrates depressed resistance. 

 Potassium and phosphoric acid opposed the unfavorable effects of nitrates with- 

 out directly raising resistance. No relation was found between resistance and 

 developmental vigor. Concentration of the soil solution depressed resistance in 

 maize, but was without effect on four other plants. No relation could be 

 established between cell sap solute concentration and resistance to cold. 



Generalizing the findings and deductions, the author states that the subtraction 

 of heat beyond the point of minimum tolerance of cold is the essential cause 

 of frost killing in case of plants. To tliis is opposed the natural resistance of 

 plant organs. The formation of ice is only an accessory phenomenon. 



Resistance is not related to cell sap concentration nor to content of acids or 

 salts, but is related to the proportion of sugar which the cell retains during re- 

 frigeration. It is thought that sugar may serve as a source of energy in respira- 

 tory combustion, or else that it may protect the protoplasm against proteolysis or 

 eventual autodigestion. 



Alterations in cellular permeability and exchange at temperatures near 

 freezing, E. Pantanelli {Atti R. Accad. Lincei, 5. ser., Rend. CI. Sci. Fis., Mat. 



