1894. NOTES AND COMMENTS. 253 



In the same journal is a resume, by J. C. Bay, of observations 

 and experiments in the formation of crystals of ice on plants. The 

 splitting of wood and the appearance of ice-crystals in the fissures 

 are phenomena well known to tree planters. As a result of the cold, 

 the tissues of the whole plant contract, and consequently their 

 turgescence is much diminished, as well as the permeability of 

 the cell-walls to water. The contents of the peripheral ends of the 

 medullary rays freeze, expand, and are pressed forward, causing a 

 split in the stem at the point of least resistance. The ice forms a 

 layer covering the whole surface of the wound. The internal pressures 

 continue to supply water, by which the ice-sheet is continually 

 augmented. 



An ancient oak formed the subject of an interesting exhibit at one 

 of the last meetings of the Linnean Society, when Mr. Carruthers 

 showed some photographs of an old tree which still grows at Con- 

 thorpe, in Yorkshire. Prints prepared some hundred years ago show 

 no departure from the normal habit of a fine oak, but recent photos 

 illustrate a remarkable change in mode of growth. The successive 

 ramifications of the thick lower branches no longer spread in all direc- 

 tions, but the latter produce a number of erect shoots giving the 

 appearance of young trees growing from the horizontal main branch, 

 which may be compared with a rootstock sending up vertical shoots, 

 as happens in the Solomon's seal, species of Polygonum, and many 

 creeping plants. 



German botanists are still busily working at the tropical African 

 flora, to which the recently-issued number of Engler's Botanisches 

 yahrbuch (vol. xix., parts 2 and 3) supplies a further contribution. 

 This includes a large number of newLabiatae, Orchids, Thymeleaceae, 

 and others. In the jfouvnal of Botany for September, South African 

 botany is represented by a paper by R. Schlechter, who describes 

 some new species of Asclepiadaceae from Natal and elsewhere. 



Some time ago we gave an account of Magnin's work on the 

 flora of the Jura Lakes. During the summer of 1893, under the 

 auspices of the Michigan Fish Commission, the flora and fauna of 

 Lake St. Clair have been studied in a similar manner. Mr. A. J. 

 Pieters, the botanist of the party, states that the flora was found 

 arranged in zones, limited by the depth of the water, each with 

 certain characteristic plants, but Magnin's Nupharetum did not 

 exist. 



News has arrived from Mr. G. F. Scott Elliot, in a letter dated 

 Ruwenzori, the 24th of May, in which he states that he has been on the 

 mountain for nearly two months, collecting and exploring under 



