ICE IN PLANT TISSUE. 3 I 



Regarding the formation of ice within the tissue, one of the first 

 detailed accounts was also by Sachs. In the first edition of his 

 " Lehrbuch " (1868) he described the appearance of ice masses 

 in the petioles of artichoke, Cyiiarca Scaly in us. In this plant the 

 bundles of the petiole are somewhat free in the tissue. On freez- 

 ing, ice cylinders, each made up of radiating ice prisms side by 

 side, were formed around each bundle. The epidermis of the 

 artichoke was usually completely separated from the remainder of 

 the petiole by a subepidermal ice layer, leaving the epidermis 

 hanging about the petiole like a loose sack when the ice had 

 melted. 



Prillieux more careftdly studied the ice masses within the 

 tissues. His conclusions were, in brief, that the large ice clumps 

 formed in plant tissue were composed of ice-needles placed close 

 together ; that the cells were not ruptured, but that often when the 

 quantity of ice was very great and the intercellular spaces were 

 not sufficiently large the cells were forced apart to accommodate 

 the large clumps. Sometimes the epidermis or bark was ruptured 

 and the lamellae of ice were protruded, thus giving rise to the so- 

 called " frost-plants."* He was also the first to affirm that the 

 sap comes out from the cell in the liquid form. He rightly stated 

 that in the case of hardy plants the separation of the cells by the 

 ice masses ordinarily causes no injury. The regularity of ar- 

 rangement of the masses for each species was found very marked 

 both by Prillieux and Kunisch, but this was to be expected since it 

 depended more or less on the tissue configuration. 



In most very fleshy structures, as in potatoes, the ice masses 

 which are usually lenticular in form lie irregularly or perhaps 

 more or less parallel to the surface. In beets, however, according 

 to Miiller-ThurgaUjthe masses, although mostly tangential near the 

 surface, are in the interior either tangential, radial, or cross-wdse. 

 In Dahlia tubers only small lenticular masses were found in the in- 

 terior, while near the periphery very large ones were present. 

 In the intermediate portion of the tuber only radial masses were 

 found. Sometimes the ice masses in these tissues reach the length 

 of a centimeter, but are usually much smaller. 



* See also MacDongal. Frost plants, a resume. Science, 22: 351-52. 

 1893. 



