Search results
Results from the WOW.Com Content Network
Heterospory evolved due to natural selection that favoured an increase in propagule size compared with the smaller spores of homosporous plants. [2] Heterosporous plants, similar to anisosporic plants [clarification needed], produce two different sized spores in separate sporangia that develop into separate male and female gametophytes.
Low-pressure phase diagram of pure iron. BCC is body centered cubic and FCC is face-centered cubic. Iron-carbon eutectic phase diagram, showing various forms of Fe x C y substances. Iron allotropes, showing the differences in structure. The alpha iron (α-Fe) is a body-centered cubic (BCC) and the gamma iron (γ-Fe) is a face-centered cubic (FCC).
Plants that are homosporous produce spores of the same size and type. Heterosporous plants, such as seed plants , spikemosses , quillworts , and ferns of the order Salviniales produce spores of two different sizes: the larger spore (megaspore) in effect functioning as a "female" spore and the smaller (microspore) functioning as a "male".
The dihydrate of iron(II) oxalate has a polymeric structure with co-planar oxalate ions bridging between iron centres with the water of crystallisation located forming the caps of each octahedron, as illustrated below. [77] Crystal structure of iron(II) oxalate dihydrate, showing iron (gray), oxygen (red), carbon (black), and hydrogen (white ...
Elemental iron is virtually absent on the Earth's surface except as iron-nickel alloys from meteorites and very rare forms of deep mantle xenoliths.Although iron is the fourth most abundant element in Earth's crust, composing about 5% by weight, [4] the vast majority is bound in silicate or, more rarely, carbonate minerals, and smelting pure iron from these minerals would require a prohibitive ...
The iron compounds produced on the largest scale in industry are iron(II) sulfate (FeSO 4 ·7H 2 O) and iron(III) chloride (FeCl 3). The former is one of the most readily available sources of iron(II), but is less stable to aerial oxidation than Mohr's salt ((NH 4) 2 Fe(SO 4) 2 ·6H 2 O). Iron(II) compounds tend to be oxidized to iron(III ...
Most non-vascular plants, as well as many lycophytes and most ferns, are homosporous (only one kind of spore is produced). Some lycophytes, such as the Selaginellaceae and Isoetaceae, [7]: 7 the extinct Lepidodendrales, [8] and ferns, such as the Marsileaceae and Salviniaceae are heterosporous (two kinds of spores are produced).
In the homosporous families Lycopodiaceae and Huperziaceae, spores germinate into bisexual free-living, subterranean and mycotrophic gametophytes that derive nutrients from symbiosis with fungi. In Isoetes and Selaginella, which are heterosporous, microspores and megaspores are dispersed from sporangia either passively or by active ejection. [8]