consequently of climate. Instances occur, as in the genera Hortonia, Mappia, Turpinia, Euonymus, Elæodendron, in which a more elevated locality produces a form or variety possessing a stouter habit and larger flower than are observed in the same species when growing only a little above the level of the sea. These forms or varieties would probably be viewed by some botanists in the light of distinct though closely allied species, and they occupy, in fact, that debatable ground the difficulties and perplexities of which the practical naturalist alone knows, and which, in the opinion of many (and I may include myself among the number), are only to be got rid of by the adoption of the views enunciated by Mr. Darwin as regards the relationship of allied forms or species by descent from a common ancestor."

Owing partly to our ignorance of the extent of the Floras of other tropical islands, and partly to the different estimates of specific limits entertained by different authors, it is not possible to compare the Ceylon Flora accurately with that of any other tropical island, except that of Jamaica, which, as we gather from Grisebach's Flora of the British West Indies, contains about 1092 species of flowering plants. The latitudes, areas, and elevations of these islands respectively are—

This comparison would not be, however, a good one, for Jamaica presents little variation of climate beyond what the elevation of the Blue Mountains afford. In Ceylon, on the other hand, Mr. Thwaites tells us that much of the variety of its vegetation is due to the great. difference of climate which the island presents. The southern part possesses a humid very hot climate, equable temperature, and considerable rainfall. The northern portion is hot and dry, being screened by the hilly interior from the rainy south-west monsoon, and enjoys but a short rainy season. The mountainous interior again presents a considerable tract of cool very rainy districts. Hence, as Mr. Thwaites remarks, the vegetation of the humid south is akin to that of Sumatra and the Malay Archipelago. That of the dry northern districts is identical with that of the Coromandel Coasts, and of the hilly interior with the Neilgherrie Mountains.

It is to be hoped that on some future occasion Mr. Thwaites will enter fully into the subject of the relations of the vegetation to the climate, and tell us how far he thinks the presence in Ceylon of

the plants of the several countries he cites as having analogous climates, may be accounted for by favouring climate alone. With regard to the peopling of the northern districts by Coromandel plants, few naturalists would, in the present state of geological belief, deny that the immigration of these may have taken place before the severance of Ceylon from the great Western Peninsula of India; and as the large Indian mammals of the island could only thus have found their way across, it is reasonable to suppose that the plants did so too. To account thus, however, for the generic and almost specific identity of the mountain temperate Flora of Ceylon with that of the Neilgherries, 400 miles distant, is not so easy, and, except a great lowering of temperature be assumed, demands not only continuous land, but a continuous mountain chain. In this case the small size of many of the seeds of the plants, common to both mountain-ranges, and other circumstances connected with their facility of transport, (direct by currents, or indirect by birds, &c.) must also be taken into account.

Far more curious and suggestive, however, than the similarity of the northern and mountain Floras of Ceylon, with those of Coromandel and the Neilgherries, is the relation of the Southern Ceylon Flora with the Malayan. This which alone would furnish materials for a most interesting discussion is evidenced by the presence of gigantic trees of Dipterocarpea, of which Order Ceylon contains 8 genera and 42 species, while in continental India there are probably not onesixth of that number; by the presence of Cycas Rumphii,* and by a great many representative and identical species, scattered through many Natural Orders. There is also a most curious relation established between Madagascar and tropical Africa and Ceylon by means of a species of Cacteæ, Rhipsalis Cassytha, the only plant of its Order found beyond the limits of America, by Angræcum and sundry other plants; to which must be added, by way of negative evidence the absence of Conifers and Cupuliferæ in both countries.

Our limits prevent us going further into detail as to the contents of Mr. Thwaites' volume, which we the less regret, from believing it to be only a precursor to a general Flora of the island, in which he will doubtless expatiate upon these and kindred topics.

We should like too to have carried out our comparison between Ceylon and the West Indies, and show all the points in which they

Discovered by Mr. Thwaites whilst the last part of his work was passing through the press

contrast, but we must confine ourselves to the most prominent, and that is the very intimate relationship subsisting between the Cingalese vegetation and that of the temperate zone to the northward of it. The West Indies, as we showed, have not on their mountains any temperate North American types; Ceylon, on the other hand, though its mountains are no higher and are situated much nearer the Equator, presents many Northern and even European plants. Of these the most remarkable are

Here then we have in Ceylon no less than 57 genera (out of 933)

which are all European, in contrast to 30 (out of 1091) in the West

Indies; and 15 Northern species in Ceylon, in contrast to 9 in the West Indian highlands.

IX.-REPORT ON SEXUALITY IN THE LOWER CRYPTOGAMIA.

Ir was at first intended in this Report to have recapitulated the principal discoveries with regard to sexuality in the Cryptogamia generally; but two reasons suggested themselves against the adoption of this course:-one was the great length to which the report must have been extended; but the other and principal reason was, that the main facts with regard to the sexuality of the Higher Cryptogamia are already accessible to the English reader in the Report of the late Professor Henfrey to the British Association in the year 1851, and in the translation of Dr. Hofmeister's Treatise on the Higher Cryptogamia, published by the Ray Society in 1862.

This Report has, therefore, been limited to what are usually styled the Lower Cryptogamia, viz., the Lichens, Fungi and Algæ.

The Lichens may be disposed of in a few words-for our knowledge as to their sexuality may really be said to be nil. The function of the small bodies called "spermatia," (which are so very generally present in special conceptacles on the thalli of Lichens), does not appear to be fecundative as has been supposed by some botanists; and the notion of their being male organs is now, we believe, very generally abandoned, although Dr. Stitzenberger, in the Ratisbon Flora for 1862, speaks of them as " männliche Befruchtungsorgane." We must, however, mention Karsten's recent statements with regard to Conogonium Andini.

At the end of his essay on Parthenogenesisare to be found some observations on the development of the apothecia in that Lichen, which, if correct, would show that the latter originate in a free central cell, contained in an organ similar to the archegonia of the higher cryptogams. This central cell he states to be impregnated in a manner almost exactly similar to what occurs in Coleochate and Saprolegnia amongst the Algae. If Karsten's observations were to be relied upon, the problem of sexuality in the Lichens would have been solved, for it could hardly be doubted that what was alleged to have been seen in Conogonium would speedily have been discovered in other Lichens, when observers were put upon the track. Karsten's observations, however, have not been confirmed by any other botanist; and Dr. Schwendener, in the Flora for 1862, meets them with a positive contradiction. We have not space to give more than Dr. Schwendener's concluding remarks; but he says: "Whether the

"mother-cells of the spores or some other cells are impregnated, is a question still unsettled, and which will probably occupy many an "observer until the right solution is arrived at. As matters stand "at present, however, the assumption of an impregnation of the "young asci is the most probable one. It is easily seen that in many "apothecia, tolerably wide canals lead down from the upper surface "of the lamina proligera to the apex of the asci; and moreover, "that the membrane of the older asci exhibits at this spot (which is “usually thickened and gelatinous), a pore, which traverses the inner “layers, extending often as far as the so-called primary membrane. May it not be suspected that these circumstances have some con"nexion with the impregnation ?"

We cannot venture to say yes or no to this inquiry: the question remains an enigma for Lichenologists, and we now pass on to the consideration of the Fungi.

The speculations as to the existence and nature of the sexual organs of Fungi have been numerous, and of the most various kind. It would be merely a matter of historical curiosity to follow out the different suggestions which have from time to time been made, and we would refer those who wish to acquaint themselves with the literature of the subject to the 9th chapter of Tulasne's "Selecta Fungorum Carpologia." Of all the speculations above referred to, that which held its ground the longest, and which is as old as the time of Micheli, is the theory which attributed sexual functions to the so-called "cystidia," which are large overgrown vesicles occurring upon the gills of many of the Agaricini, as well as upon Boletus. The idea of the sexuality of these organs has been supported by Bulliard, and (long after him) by Klotzsch; but of recent writers, Corda has been the most decisive in its favour. He called the organs in question antheridia or pollinaria, and considered each of them equivalent to a pollen-grain: he thought that a granular fluid emerged from their apices, the diffusion of which stimulated the formation of spores. He was of opinion that the antheridia differed so much in their structure and partial distribution from the paraphyses of the Ascomycetes that the two could not have the same function. Phoebus,* on the other hand, alleges that the cystidia are a peculiar kind of altered paraphyses or basidia, and that although they are more often absent from the Agaricini than paraphyses are from the ascophorous stratum

• Nova Acta, vol. xix. and Deutschland's Kryptogamische, Gift-gewächse. N.H.R.-1865.

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