A Grammatical Dictionary of Botanical Latin

Hypothallus,-i (s.m.II), abl. sg. hypothall: hypothallus [> Gk. hypo-, below, under, beneath, lower, basal + thallos (s.m.II), a young shoot, a young branch, thallus]; cf. protothallus,-i (s.m.II), q.v., abl. sg. protothallo;

of lichens: “delicate filaments which constitute the vegetation of Coniomycetous Fungals. The inferior stratum of the thallus of Lichenals” (Lindley); “the marginal outgrowth of hyphae in crustaceous Lichens” (Jackson); “(of lichens), the first growth of the hyphae; “1. a marginal outgrowth of hyphae from the thallus in crustose lichens (WIII); (of lichens) the first growth of the hyphae, before any differentiation has taken place, often persisting as a colored layer below or surrounding a few lichen thalli; (of the genus Balansia at least) applied by Diehl (1950) to the pseudomorph or “sclerotium” or “pseudosclerotium” of others” [i.e. of other authors] (S&D); “crustose lichens may have a hypothallus - i.e. an algae-free mat of hyphae extending beyond the margin of the regular thallus;” = protothallus,-i (s.m.II), q.v.

Lichen genus Lepraria: “Throughout these keys the term “hypothallus” refers to the layer of fungal tissue that underlies the lichenized granules. The thickness of a given thallus is due to the thickness of the hypothallus. Species with a thin hypothallus are those typically referred to as having a thallus that is “dispersed”, “lacking a medulla”, or “thin and continuous”. Similarly, species with a thick hypothallus are those that are typically referred to as having “a medulla”. Differences in the presence/absence of a well developed pseudocortex on the thalline granules are also used to distinguish taxa .... Species in which the granules have a well developed pseudocortex do not appear “fluffy” or “cottony” and are almost all are members of the L. caesioalba-neglecta group. The granules of these taxa have a characteristic gestalt because they are corticate and compact instead of ecorticate and composed of loosely intertwined hyphae” [Notes on Lepraria s.l. (Lecanoromycetes, Ascomycota) in North America: New species, new reports, and preliminary keys James C. Lendemer Brittonia September 2010, Volume 62, Issue 3, pp 267–292.

- hypothallo nigro, profuso, with the hypothallus black, out-spread.

- [lichen] facie fere ut in Lecidea petraea thallo albicante), subiculo (hypothallo?) nigro (Nyl.), almost with the appearance as in Lecidea petraea with a whitich thallus, with the subiculum (hypothallus?) black.

of Myxomycetes (the slime molds), the thin layer on the surface of the substratum not used up in sporangium development” (Ainsworth & Bisby); “2. a residue like a film that remains after the formation of sporangia in slime molds of the class Myxomycetes” (WIII); “(Of Myxomycetes) [slime molds] a sheetlike film, or a more or less continuous net, spreading beneath the sporangia and upon which the sporangia rest (S&D); “The hypothallus is a hat-like layer on true slime molds, the myxogastria, on which the fruit body is sitting and which displays the connection of the fruit body to the underground. The hypothallus is produced by the plasmodium at the beginning of the fructification. Depending on the species, it can be membranous to thick or tender to solid and nearly transparent to radiant coloured. It is either shaped isolated as an edge of single fruit bodies or as a permanent layer, which connects the edges of numerous fruit bodies. In some but rarely cases it is missing entirely (Wikipedia Sept 2016):

- [Diderma brooksii Kowalski), sporangiis dissipatis vel gregariis, sessilibus vel breve stipitatis, globosis; hypothallo generaliter conspicuo, albo, calcareo; peridio duplici, pariete extremo calcareo, crustaceo, pariete interno ab extremo discreto; stipite, quandocumque presenti, extensione hypothalli, with the sorangia dispersed or gregarious, sessile or shortly stalked, globose; with the hypothallus generally conspicuous, white, calcareous; with the peridium double, with the outermost wall calcareous, crustaceous, with the inner wall separated from the outmost; with the stipe, whenever present, by an extension of the hypothallus.

- [Diderma] sporangiis gregariis, sessilibus, hemisphaericis vel paulo elongatis, chalybeis; hypothallo inconspicuo, with the sporangia gregarious, sessile, hemispheric or somewhat elongate, chalybeous [i.e. iron- or steel-gray]; with the hypothallus inconspicuous.