Fig. 332.
Details of microspore and male prothallium of selaginella; 1st, microspore; 2d, wall removed to show small prothallial cell below; 3d, mature male prothallium still within the wall; 4th, small cell below is the prothallial cell, the remainder is antheridium with wall and four sperm cells within; 5th spermatozoid. After Beliaieff and Pfeffer.
587. Female prothallia.—The female prothallia are developed from the macrospores. The macrospores when mature have a rough, thick, hard wall. The female prothallium begins to develop inside of the macrospore before it leaves the sporangium. The protoplasm is richer near the wall of the spore and at the upper end. Here the nucleus divides a great many times, and finally cell walls are formed, so that a tissue of considerable extent is formed inside the wall of the spore, which is very different from what takes place in the ferns we have studied. As the prothallium matures the spore is cracked at the point where the three angles meet, as shown in [fig. 334]. The archegonia are developed in this exposed surface, and several can be seen in the illustration.
Fig. 333.
Section of mature macrospore
of selaginella, showing female
prothallium and archegonia.
After Pfeffer.
Fig. 334.
Mature female prothallium of
selaginella, just bursting
open the wall of macrospore,
exposing archegonia.
After Pfeffer.
Fig. 335.
Seedling of selaginella still
attached to the macrospore.
After Campbell.