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POPULAR SCIENCE REVIEW. 
the Anthropological Commission appointed to investigate the Shetland 
Islands, has given us a valuable and elaborate account of their flora. The 
facies of the flora of these islands is, he tells us, very striding ; especially 
so on the land-slopes bordering the sea ; for they are rich in plants which 
are more abundant in petals than in leaves. This profusion of flowers he 
believes to be in accordance with the operation of a law that, in proportion 
as the habitat of a plant becomes ungenial, and thus threatens to exterminate 
the species, the flowers increase in number and in size. Mr. Tate has care- 
fully compared his own observations with those of other writers, and sums 
up the results of his explorations as follows : — The flora of Shetland, in its 
present revised form, numbers 364 indigenous species, and 14 marked indi- 
genous varieties. With the following exceptions, all are generally distributed 
throughout Central Europe, and are found in Great Britain. The exceptions 
are Cerastium Fdmonstoni , Lathyrus acutifolius, which are restricted to the 
island of Unst ; Arenaria Norvegica, also confined to that island (the most 
northern and eastern of the Shetland group), but elsewhere only known in 
Scandinavia. The only boreal plants are Cherleria sedoides, Arenaria Nor- 
vegica, and Saussurea alpina ; Geranium phceum is doubtfully native. Even 
alpine forms are poorly represented in these isles, and the majority of these 
are confined to Konas Hill. Of the six Saxifrages, 8. stellaris, 8. nivalis, 
8. rivularis, S. caespitosa, S. oppositifolia, and S. hypnoides, which range from 
Scotland to the Feroes, Iceland, and Greenland, only 8. oppositifolia is a 
Shetland plant (yet occurring at the opposite extremities of the mainland). — - 
Vide Journal of Botany, January. 
The Fertilization of Tigridia. — Dr. Martin Duncan has contributed to the 
Microscopical Journal a most noteworthy memoir upon the structure and 
function of the essential parts of the flower in one of the Iridacese. The 
observations as to the structure of the parts examined deserve the attention 
of structural botanists. The experiments conducted upon the fertilizing 
organs are also of extreme interest. Several of these are minutely recorded, 
and in summing up their results, Dr. Duncan draws the following among 
other interesting conclusions : — From these experiments it is proved that the 
impregnation is perfected in a little more than twenty-four hours ; that the 
pollen-grain produces a tube-cell, which grows according to the manner of 
cells, which passes through stigma, style, and to the remotest ovule in the 
ovary — a space oftentimes of five inches — in twenty-four hours ; that, taking 
the average length of the tissue to be perforated to be four inches, the pollen- 
tube grows at the rate of one inch in six hours ; that before the pollen-tubes 
are halfway down the style, if their connection with the pollen-grain be 
destroyed, they still grow and impregnate ; that after the pollen-tube has 
fairly entered the style, it is independent, both as regards its subsequent 
growth and impregnating properties, of the pollen-grain ; and that the varying 
conditions of the atmosphere influence the rapidity of the growth of the 
pollen-tube, and consequently impregnation. — Yicle the Quarterly Journal 
of Microscopical Science, January, 1866. 
