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Show ANNOTATIONS AND ADDITIONS. 357 From the tropics (where in the great continents D'Urville estimates the ratio generally at 1 : 20) we see the relative frequency of ferns decrease rapidly in the temperate zone. The quotients are : for North America and for the British Islands 3~, for France 5\, for Germany j 2 , for the dry parts of the south of Italy -/4 , and for Greece ·h· Towards the colder regions of the north we sec the ?"elative frequency increase again rapidly j that is to say, the number of species of ferns decreases much more slowly than does the number of species of phrenogamous plants. At the same time, the luxuriance, abundance, and mass of individuals in each species augments the illusive impression of absolute numbers. According to Wahlenberg's and Hornemann's Catalogues, the relative numbers of Filices are, for Lapland ln for Iceland -f8 , and for Greenland -f2 . Such, according to the present state of our knowledge, are the natural laws manifested in the distribution of the pleasing form of Ferns. But it would seem as if in the family of Ferns, which has so long been regarded as a cryptogamic family, we had quite recently arrived on the traces of another natural law, a morphological one of propagation. Count Leszczyc-Suminski, who happily unites the gift of microscopic examination with distinguished artistic talent, has discovered in the prothallium of ferns an organization by which fructification is effected. He distinguishes a bisexual arrangement in the ovule-like cell on the middle of the theca, and in the ciliated antheridia or spiral threads before examined by Nageli. The fertilization is supposed to take place not by pollen tubes but by the movable ciliated spiral threads. (Suminski zur Entwickelungs;geschichte der Farrnkrauter, 1848, s. 10-14.) According to this view, Ferns, as Ehrenberg expresses it (lVIonatl. Berichte der Akad. zu Berlin, .J anuar 1848, s. 20), would be produced by a microscopic fertilization taking place on the prothallium as a receptacle j and throughout the whole remainder of their often arborescent development they would be :flowerless and fruitless plants, forming buds or bulbs; the spores or sori on the under side of the frond not being seeds but flower buds. (~9) p. 244.-" Liliacece." The principal seat of this form is Africa, where it is both most varied and most abundant, and where these beautifully :flowering |