30 REPORT ON BOTANY, MDOCCXLI : 
paper, entitled, ‘‘ Micrometrical Determinations and Microsco- 
pical Researches, by P. Harting.” Many micrometrical deter- 
minations of vegetable objects are contained in this treatise, 
of which I will only enumerate some, because the whole table 
would otherwise have to he copied here. They are stated in 
ten thousandth parts of a millimeter. The smallest spiral 
vessels from the chalaza of an oak, impregnated within a few 
days, measured 33 ten-thousandths of a millimeter ; the thick- 
est, from a twig of one year old of Samhums nigra, 425 ; the 
thinnest from the same, 140 ; the spiral fibre from the former, 
the thickest, 39 ; from the latter, the thinnest, 27. The 
average diameter of the dots, on the dotted spiral vessels from 
the same twig, 48. Rings from an annular duct in the same 
twig, average diameter, 38. Stomate of a tolerably large leaf of 
Lilium candidum, average length, 712 ; average width, 520 ; 
average length of the slit, 420 ; average width, 123. Stomate 
of a matured leaf of Leontodon taraxacum, average length, 
230 ; average breadth, 130. Stomate of a matured leaf of 
Lemna minor, average length, 192 ; average breadth, 160 ; 
average length of the slit, 142 ; average breadth, 90. Pollen 
granules of Malva rotundifolia, 1341 : of Lilium candidum, 
average length, 925 ; average breadth, 392 : of Lathyrus odo- 
raius, average length, 517 ; average breadth, 283 : of Salix 
alba, average length, 272 ; average breadth, 126 : oi Lamium 
purpureum, average length, 412 ; average breadth, 248 : La- 
mium album, average length, 308 ; average breadth, 202 : of 
Aconitum Napellus, average length, 83 ; average breadth, 47. 
Chlorophill grains from a leaf of Sambucus nigra, average 
diameter, 50 : of CJielidonium majus, 55 : oiSedum telephium, 
67 : of Geranium robertianum, 52 : of Malva rotundifolia, 
51: of Iris pseudacorus, A2 \ of Lilium candidum, 30: of 
Georgina variabilis, 34 : thickness of the layers of a grain of 
potato starch, 8-30. Although some uncertainty always takes 
place in micrometrical measurements, these statements are, 
nevertheless, very valuable as proportional numbers ; and it 
is therefore very desirable, that the same observer should con- 
tinue his observations with the same instrument. The num- 
ber of animal objects which were measured is much greater 
422 
