510 Transactions of the London Horticultural Society. 



ticity of its vegetable membrane, and frozen fruit becomes, as we know, very 

 much shrivelled. Each cell, therefore, acts like a bottle of frozen water, only 

 there is no bursting, because the membrane is extensible.' 



" But when plants, easily killed by cold, are exposed to so low a temperature 

 as that just described, it is to be feared that phsenomena actually connected 

 with the destruction of vegetable life may be intermixed with others, which 

 merely indicate the physical effects of cold upon vegetable matter already dead. 

 For the purpose of judging how far this conjecture is well founded, I have 

 carefully examined the post mortem appearances of several plants killed by ex- 

 posure to a temperature artificially reduced only to from 28° to 30° Fahren- 

 heit. These observations, while they have confirmed the general accuracy of 

 Professor Morren's statements, have led to other conclusions which also ap- 

 pear important. 



" I could not find the vesicles of cellular tissue separable from each other, 

 even in the most succulent species submitted to experiment, and I conclude 

 that this circumstance, to which Professor Morren attaches importance, and 

 to which M. Payen ascribes the difficulty of extracting starch from frozen po- 

 tatoes, is not so much connected with the destruction of vegetable life as a 

 result produced upon the tissue by a great intensity of cold. I did, however, 

 find it lacerated in several cases, as if by the distension of the fluid it had 

 contained. In a Stapelia the whole of the cellular tissue was soft, and de- 

 formed, as if it had been extended, witli but little power of recovering itself 

 again, and several large irregular lacerated cavities were observed. The same 

 appearances were remarked in Euphorbia Tirucalli, but the laceration of the 

 tissue was much less extensive. In Hibiscus Rosa Sinensis the cells of the 

 cortical integument (mesophloeum) werevery much torn, and in Hibiscus mili- 

 taris not only the cells of the bark, but especially those of the pith, were so 

 completely broken up, that it was difficult to obtain a thin slice of those parts 

 for examination. In no case, however, have I found any kind of tissue rup- 

 tured, except the soft cellular dodecahedral or prismatical. It would also 

 seem that M. Payen recognises the laceration of tissue by frost, for he ascribes 

 the acridity of frozen potatoes to an extravasation of the acrid matter which 

 exists in the epiphloeum of such tubers, and which, in a natural state, is locked 

 up in the cells of which that part consists. Independently of these ob- 

 servations, it is not to be doubted that frost does split the tissue of plants. I 

 saw the youngest shoots of Erica mediterranea, cinerea, and others, shivered 

 into thousands of pieces in the Horticultural Society's Garden, on the morning 

 of the 20th of January. The branches of Melaleucas were rent to their points 

 at Carclew. Several cases, among others that of the common holly, were ob- 

 served at Claremont, where the bark was split, and rent asunder from the 

 wood below it ; and Sir Oswald Mosley has given me the following instance, 

 which occurred under his own observation. ' An oak tree, growing upon the 

 south side of a hill, in a sheltered situation, in Knightly Park, near Burton- 

 upon-Trent, in the county of Stafford, was rent in the severe frost of last 

 winter in two different places, to the height of 13 ft. 3 in. There was an in- 

 terval of 11 in. between the two shakes, which were each of them one quarter 

 of an inch wide, and extended in depth to the heart of the tree. The girth of 

 the tree is 6 ft. 10 in., and as soon as the frost went the openings closed again, 

 and the tree is now as flourishing as ever.' To these cases many more might 

 be added. 



"The organisation of woody tissue appears to be affected, but not by 

 laceration. If a frozen and unfrozen transverse slice of the stem of Hibiscus 

 Rosa Sinensis be placed, side by side, upon the field of the microscope, it is 

 obvious that the diameter of the tubes of the v/ood and liber is considerably 

 less in the former than in the latter ; this appears to be owing to an increase 

 in the thickness of the sides of the tubes, which has the effect of diminishing 

 their calibre. 



" The expulsion of air from aeriferous organs, and the introduction of it into 

 parts not intended to contain it, is a striking phaenoraenon. Every one must 



