from The American Heritage® Dictionary of the English Language, 4th Edition
- n. A small, flat, delicate structure produced by a germinating spore and bearing sex organs. It is the gametophyte of ferns and some other plants.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. A prothallium.
from the GNU version of the Collaborative International Dictionary of English
- n. The minute primary growth from the spore of ferns and other Pteridophyta, which bears the true sexual organs; the oöphoric generation of ferns, etc.
from The Century Dictionary and Cyclopedia
- n. Same as prothallium.
The spores germinate and mature into a small plant called a prothallus which is the area for sexual reproduction.
The prothallus is the gametophyte generationof a fern.
At the end of six weeks or so the prothallus will perhaps appear, certainly in a week or two more; perhaps from unforeseen circumstances not for three months.
Sometimes the prothallus itself buds directly from the frond without spores, for which process the term apóspory is used.
Soon after the sporophyte can do that the the prothallus dies.
In ferns the prominent generation is the sporophyte, the inconspicuous prothallus is hardly noticed and often overlooked or mistaken for a leave on the ground.
When the proper conditions present themselves the spore germinates into a one cell layer thick, heart shapped prothallus.
On the underside of the prothallus rizoids devalope to absorbe water and minerals.