According to threergroup, a special substrate independent of the earth and water is what parasites find on living organisms, as are a large number of fungi and bacteria: among the phanerogams we remember the Cytinus hypocistis , the only European Citinacea that parasites some species of Cistus of the Mediterranean scrub ; the strange Cynomorium coccineum, the only European Balanophoracea parasite of various halophilous-hygrophilous in Malta, Sicily, Sardinia and some other isolated station; mistletoe and loranthus on various tree plants; the numerous Orobancaceae, all parasitic, and the several native and exotic Cuscute, some very harmful to the Prato plants. Epiphytes are limited by us to bryophytes and lichens and, as far as higher plants are concerned, the occasional epiphytes that A. Béguinot and GB Traverso designated with the name of arboreal trees that form small hanging gardens especially on salts and mulberry trees characteristic of the landscape are frequent. Po Valley.
It is also necessary to take a quick look at the past of our flora and the events that led it, following changes in climate and land, to its current layout and structure.
As regards the Mediterranean region, phytopaleontology has shown that in the Mediterranean and finite territories, naturally with a very different configuration from the present, there were in the Tertiary sector and especially from the Neogene here (the most numerous and instructive examples come from the rich phyllite deposits of France southern) several species identical or closely related to those that make up the ever-growing woods and scrubs, such as the oaks of the holm oak, cork oak, coccifera group, oleander, myrtle, two pistachias similar to P. lentiscus and to P. terebinthus, the phillyrea, the siliquastro, the dwarf palm, a group of genera that today form the forests of the Laurinee in the Canary Islands, such as Laurus , Persea , Ilex , Notelaea , Oreodaphne , Celastrus of which the common laurel ( L. nobilis ) similar to the living L. canariensis which held us until the late Quaternary, and in all probability the Arbutus unedo similar to A. canariensis and the Erica arborea although they grow in those woods, but have not been found up to now in the fossil state. The lack of species of the genus Cistus is also surprisingtoday so widespread, the scarcity of phyllites referable to the olive tree, to the dwarf palm and in general to the now dominant sclerophylls: but this is probably due to the fact that the lower areas, therefore closer to the fossilization sites, were populated by vegetation at all different and then largely disappeared composed of representatives of families belonging to the hottest parts of the globe (Mimosacee, Sapotacee, Malpighiacee, Combretacee, Sterculiacee, many Palms, etc.), while the current sclerophylls had to remain confined in dry and sunny areas of mid-mountain. However, the presence in the Tertiary of many constituents of the Mediterranean flora is ascertained by the numerous paleoendemisms, many of which are monotypic, from the species with disjointed and fractionated areas including in the number those and those vegetating in elevated areas and the same hypsophytes that have Mediterranean origin. Perhaps in no sector the archaic imprint is so evident as in Sardinia and Corsica and this is due to the ancient definitive emergence of those islands which are the most conspicuous remains of a configuration of lands and seas different from the present one. but no less in the state of relative isolation in a geologically recent epoch when the continental masses and the peninsulas themselves underwent those profound floristic changes that characterized the Quaternary. The first reason, which is connected with the well-known hypothesis of Tyrrhenis or Tirrenide, tells us how they were able to enrich themselves, the second how they were able to preserve so many paleoflora survivors, but this does not exclude that they too have received some recent, albeit limited infiltrations.
The thermal crises and in general the profound climatic changes that characterized the Glacial and the immediate Postglacial have affected the southern side of the Alps, and, albeit to a lesser extent, the entire peninsula, not excluding the coastal districts or near the coast. Crucial evidence lies in the results of vertebrate study of numerous caves, when thoroughly explored, which show the replacement of warm Quaternary hippo, Merck’s rhinoceros, and ancient elephant fauna with a diverse fauna. mixture of arctic types, of elements of steppe and forest that suggests in the various regions of the peninsula including the southern districts (a typical example the Romanelli Cave in the Lecce area) a vegetation in which the conditions of the tundra and steppe were respectively possible and probably at different times differently extended and of woodland formations typical of the mountain area, the first two testifying to a continental climate and the second to an accentuated rainfall and, therefore, to an oceanic climate. The glacial peaks caused the disappearance of almost all tropical types of the Tertiary, even more recently, the descent towards the coast of the evergreen scrub and its setting aside in privileged districts, the emigration of alpine and alpine ipsophytes to the high mountains of Sicily. boreali (remember the the first two testify to a continental climate and the second to an accentuated rainfall and, therefore, to an oceanic climate. The glacial peaks caused the disappearance of almost all tropical types of the Tertiary, even more recently, the descent towards the coast of the evergreen scrub and its setting aside in privileged districts, the emigration of alpine and alpine ipsophytes to the high mountains of Sicily. boreali (remember the Betula aetnensis simple breed of white birch), the descent into the plains of microthermal species since southern Lazio in the Pontine Marshes ( Deschampsia caespitosa , Rhynchospora alba , Eriophorum latifolium , Caltha palustris ). It seems logical to admit that under the empire of these conditions the exchange took place, perhaps favored by the so-called Adria, between the orophilic flora of the Balkan and that of the central and southern Apennines, as a result of which those affinities that pre-existed to the Quaternary became more intimate and close and this without the need to admit that the connection was made from very high lands, and therefore itself too hypothetical. The presence in the subalpine area of Sardinia and Corsica of Alnus suaveolens so similar to the green alder of the Alps, and that of several mid-mountain nemorals ( Anemone hepatica , Saxifraga rotundifolia , Sanicula europaea , Adoxa moschatellina , Asperula odorata, etc.) suggest relationships of continuity or at least of greater proximity of those islands with the mainland with the interlude of the Tuscan islands coinciding with a rain phase: but it must have been a very weak and fleeting interference if we keep in mind how many few elements of the warm and cold Quaternary fauna managed to penetrate the Corsardegna.