| 单词 |
prothallium |
| 释义 |
‖ prothallium Bot.|prəʊˈθælɪəm|
Pl. prothallia.
[mod.L., f. pro-2 1 + Gr. θαλλίον, dim. of θαλλός: see prothallus, thallus.]
In vascular cryptogams (ferns, horsetails, club-mosses, etc.), A minute cellular structure or thallus, produced by the germination of the spore, and bearing the sexual organs (antheridia and archegonia); forming the first of the two alternate generations, much simpler than, and as it were introductory to, the fully-developed (asexual) plant. (Sometimes including also the similar protonema of mosses.) Also, a homologous structure in the development of certain gymnosperms.
1858Carpenter Veg. Phys. §402 This Marchantia-like expansion has received the name of prothallium, and it is on this little membranous body, that the archegonia and pistillidia make their appearance. 1872Oliver Elem. Bot. ii. 286 From the germinating spore [of Ferns] arises a small, green, leafy expansion, called a prothallium, which gives off delicate root-fibres from its under surface. 1875Bennett & Dyer Sachs' Bot. 335 In the Ferns and Equisetaceæ the prothallium resembles the thallus of the lowest Hepaticæ. 1892J. B. Farmer in Ann. Bot. VI. 213 (title) On the occurrence of two prothallia in the embryo sac of Pinus. 1935C. J. Chamberlain Gymnosperms xiii. 309 In some heterosporous pteridophyte ancestor [of the conifers], the prothallium (gametophyte) became included within the spore..and finally disappeared entirely. |
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