Polypodium cambricum, it adapted to cold for to survive

This beautiful fern, so abundant in the western Mediterranean, is the descendant of a tropical Polypodium from Asia, spread over millions of years throughout Europe and North Africa, when the northern hemisphere had a tropical climate. Later, when the weather cools, some of their descendants became extinct, surviving only Polypodium cambricum, who took refuge in warm, humid microclimates in the Mediterranean region. A subsequent warming allowed to leave their shelter and settle throughout the western Mediterranean, arriving in their expansion into the British Isles. Precisely there, in Wales, which in classical Latin was called Cambria, comes the name of Polypodium cambricum. It is a fern with a diploid chromosome number of 2n = 74.

 

Vigorous specimen of Polypodium cambricum, photographed in the Serra de Tramuntana of Mallorca Island, where is one of the most common ferns. The construction of terraces to retain the land on the slopes of the mountains benefited it greatly, as this is its preferred habitat.

Numerous specimens of Polypodium cambricum on a wall of a terrace in the Sierra de Na Bourgeois, close to Palma de Mallorca, with a lush natural vegetation.

Young Polypodium cambricum photographed in the extraordinary Parque Natural de los Alcornocales in the province of Cadiz, growing on rich humus formed by decomposed leaves of old cork oak, Quercus suber. The fronds of Polypodium cambricum can reach a length greater than 50 cms. The lamina is greater than the petiole and has a form of ovate-oblong to ovate-triangular, sometimes clearly deltoidea, with pinnae usually attenuated at the apex and edge subentire or serrulated, the basal pair reflex in another plane, as can be seen in the largest frond of specimen of the photo.

Old Polypodium cambricum photographed at the Natural Park Sierra de Grazalema, a true paradise on earth with an extraordinary rich flora located in Andalusia. In the frond on the left tell it the characteristic basal pair of pinnae reflex upward.

Vigorous specimens with fronds over 50 inches growing on a wall in a garden patch of the Soller Valley on the Island of Mallorca. This fern also grows as an epiphyte on tree branches in humid environments. In the summer enters aestivation, its fronds are dried, leaving the rhizome pending the first autumn rains, then sprouting new fronds.

Polypodium cambricum, with the exception of the Balearic Islands, share the habitat with the Polypodium vulgare, an allotetraploid hybrid fern of Asian origin, the product of crosses between the Polypodium virginianum and the Polypodium glycirrhiza, which colonized Europe millions years later of Polypodium cambricum. Both ferns were hybridized, resulting in a triploid sterile hybrid called Polypodium x fontqueri, which had a mutation in the gene encoding the meiosis, called apomeiosis (no meiosis), resulting in triploid spores, which germinate to generate triploid gametophytes and these were triploid gametes, which, after fertilization, giving rise to alohexaploid hybrid Polypodium interjectum.

One of the features which distinguish the Polypodium cambricum of others Polypodium is the presence of a filamentous epidermal formations than trichomes, called paraphyses, which are located in the receptacle of the sorus of Polypodium cambricum, both in the Mediterranean subspecies as the Macaronesian. These filaments are much branched, with its length substantially greater than that of the sporangia. Their number in each sorus usually varies between 5 and 10 paraphyses.

 

Another branched paraphyses typical of Polypodium cambricum sori. Polypodium vulgare and its hybrid Polypodium interjectum paraphyses lacking. We can see by looking a sorus at a microscope, protruding above the sporangia. Its function is unknown.

 

On the underside of the pinnae are some mouth-shaped cells, called stomata, which open or close depending on the degree of humidity, to prevent or allow the flow of water through transpiration. Its function is similar to human skin pores. The photo shows the odd-shaped cellular structure puzzle, so that each cell fits into neighboring cells. (Double click on the photo to enlarge)

 

Rhizomes covered with paleae, which protect them from dehydration, sunstroke and frostbite.

 

Detail of a rhizome of Polypodium cambricum covered by paleae linear-lanceolate, ferruginous, 5 to 16 mm. long. The appearance at first sight recalls the wooliness of muskoxen and mammoths.

 

Turning to a frond sori are without indusium, distributed in two rows on the underside of each pinna along the midrib.

Double clicking on the picture to enlarge You can see details of the sori naked without covering them indusium formed by numerous yellow sporangia in different stages of maturation, photographed in February.

 

Detail of sori with mature sporangia, some already deployed, initiating the dispersal of spores in late winter.

 

Microscopic photograph of a sorus in which by transparency can be seen the spores contained in each of the sporangia. (Double click on the photo to enlarge)

 

Polypodium cambricum sporangium already deployed after the dispersal of spores. In the center of the image is the ring of thickened cells, whose number can vary from a minimum of 4 and a maximum of 18, but generally is around 7 cells.

And finally in this microscopic image made at 400 increases are reniform spores of a color similar to honey with the warty surface or perispore.

Xanthoria parietina, the lichen of gold

Xanthoria parietina is a lichen that under conditions of strong sunshine and low humidity has a nice golden color, as if formed by bits of gold leaf glued together as more or less rounded rosette of no more than 10 cms. in diameter. Belongs to the family of the Parmeliaceae.

Usually grows on the bark of trees in nutrient-rich alkaline pH, but his versatility allows him to live on superificies as diverse as limestone, roofing, asparagus and, most amazing, animal bones clean of flesh after putrefaction, by hunger for minerals.

 

Pelvis bone of a dead sheep colonized by Xanthoria parietina, in a sunny dry scrubland south of the Island of Mallorca. (Double click on the photo to enlarge)
Like all lichens are formed by the intimate symbiotic union between an alga and a fungus. The alga or phycobiont brings energy from photosynthesis, while the fungus or mycobiont provides water and minerals. Many millions of years ago learned to live together, helping each other, allowing them to successfully colonize the new land emerging from volcanic eruptions and tectonic plate movements. In fact, lichens are often the first living organisms to colonize the volcanic islands just after the lava cooled.

 

Femur of sheep with several Xanthoria parietina that have come together in exuberant growth by nutrient-rich bone. Particularly striking is the lack of growth in the non sunny bone, by the need for sunlight of symbiotic algae, whose chlorophyll depends on sunlight for photosynthesis.

The other femur of the same sheep with Xanthoria parietina only on the side facing south. Note the extreme aridity of the garrigue soil, cracked and scorched by the hot summer sun of Mallorca. These harsh conditions do not appear to have any effect on lichen, quite the contrary, by its acute heliophilia and thermophilia.

Greater trochanter and lesser trochanter covered by lichen. On the head of the femur can see two tiny Xanthoria parietina newly germinated. Double click on photo to enlarge it, you see the orange apothecia fruiting bodies that are developed by the fungus or mycobiont, which produce ascospores for sexual reproduction. The alga or phycobiont can not reproduce sexually and his cells called gonidia are attached to the ascospores, so that when they germinate and form hyphae or fungal filaments in a network, the algae cells are placed in the hollow of the hyphae growing together in symbiosis.

Xanthoria parietina covering the south side of the bark of a young pistachio, Pistacia vera, in the middle of August, in an orchard in the Valley of Soller on the island of Mallorca.

Xanthoria parietina pistachio same earlier in the month of December with the detail of their fruiting bodies or apothecia. (Double click on the photo to enlarge)

Curious growth of Xanthoria parietina on the internodes of Asparagus albus, in the property Na Riera  of Algaida Village, located in the center of the Island of Mallorca.

Beautiful Xanthoria parietina growing on the roof of PVC in a greenhouse in late December.

Xanthoria parietina growing on Echinopsis atacamensis ssp. pasacana in the magnificent Botanicactus of Ses Salines in southern of Mallorca.

 

Young Xanthoria parietina on the bark of Acer negundo a greenish color to grow in the shade of the bark of maple with a lot of humidity.

Close-up image of Xanthoria parietina growing on the same maple of previous photo with the detail of the apothecia of mycobiont at different stages of maturation. (Double click on the photo to enlarge)

 

Vigorous Xanthoria parietina with lush growth on the bark of an elder tree, Sambucus nigra. The intense green color is due to the humidity of the porous elder tree bark, which acts like a sponge, retaining rainwater, so get a hearty lichen water intake. 

 

And finally in this picture you can see a group of Xanthoria parietina growing on a moist, shaded boulder in a thick oak forest of the Serra de Tramuntana in Mallorca. It is appreciated that acquires greenish lichen in these wet conditions and poor light.

This lichen was used in ancient pharmacopoeia for treating malaria with the name of lichen parietinus as a substitute for cinchona bark. It was also used as a dye for dyeing yellow and brown because it contains parietina.