 Description： |
Mycelium spissum, breve, quod abundantes in Cammabis staivae seminibus gignitus. Hyphis plerumque non ultra 8.0 mm. longis, crassis, et ad vasim ramosis; mediis hyphis hyphis plerumque 24 μ diam. Sporangiis cipiosis, clavatis in longis cylindricalibus, 350 μ longis, 20 μ diam; terminalibus, cymosis. Aliquibus sporangiis Achlya instar; plerumque truiireticulis formis. Oogoniis globosis, 21-30 μ, plerumque 26 μ diam, tunica oogoniorum non-punctulatis. Oosporis 1, plerotic, guttulis oleosis excentrice. Antheridiis androgenus, grocilibus, multis in oogoniis applicatis. Mycelium depauperate, forming a dense growth on hempseed. Hyphae usually not more than 8.0mm. long, averaging 24 μ in diameter near the center; delicate and branching. Sporangia abundant, terminal, clavate to long-cylindrical, 20-30 × 200-550 μ, averaging 20 × 350 μ; generally 3-5 spores wide, not branching. Secondary sporangia arising by cymose branching: a few of the early sporangia under favorable conditions, discharge spores as in Achlya, in older cultures the majority of the sporangia are of the true-net type Ⅰ and very rarely brevilegnoid type. Gemmae rare, terminal or intercalary; single or catenulate. Oogonia abundant, spherical rarely subspherical, 20-30 μ in diameter of the oogonium, often branch. Oospore single, plerotic, eccentric. Antheridial branches androgynous, always wrapping about the oogonium. Autheridia up to 8 μ thick. Antheridial branches not developing sporangia. Oospores genminating by short or longer, slender, unbranched germ tubes, bearing small clavate true net I sporangium. |
| Note： |
Indoh (1941) erected a new species Brevilegnia variabilis, which differs from its allied species Brevilegnia bispora Couch and Brevilegnia parvispora H?hnk by possessing true net type dictyuchoid sporangia. This characteristics was found in the genus Dictyuchus, not in Brevilegnia. So Johnson (1975) suspected that B. variabilis was a species of Bictyuchus. Indoh’s B. variabilis was not satisfactorily illustrated. Nevertheless from his description and two figures, we found that our isolate is very similar to his isolate by possessing plerotic oospores, dictyuchoid and achlyloid type sporangia being observed, androgynous antheridial branches wrapping about the oogonium, and locking large irregular antheridia. Concurrently we observed many true net type Ⅰ sporangia with persistent sporangial wall in germination oospores and older culture. Therefore we believe that our isolate and Indoh’s are the same species and it is logical to transfer this species to Dictyuchus. Dictyuchus variabilis possesses characteristics which relate it more closely to Dictyuchus pseudoachlyoides Benenk, than to the other species of Dictyuchus. This species differs from D. pseudoochlyoides in possessing plerotic oospores, smaller oogonia, which wrapping about by a recurved antheridial branch. The plerotic oospore is rarely found in family Saprolegniaceae. |
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Phylum：Oomycota >> Class： Peronosporea >> Order： Saprolegniidae