Capillitial Development in the Myxomycetes Badhamia Gracilis and Didymium Iridis

SUMMARY

The development of the capillitium of two species of Myxomycetes, Badhamia gracilis (Macbr.) Macbr. and Didymium Iridis (Ditm.) Fries, has been investigated. In Badhamia gracilis it was found that the capillitium develops as a result of anastomoses between tubular invaginations from the inner peridial walls and the central vacuoles resulting from protoplasmic condensation. The vacuoles and invaginations in B. gracilis become filled with excretory products, some of which remain as calcium carbonate after the water evaporates. The capillitium in Didymium Iridis also is formed by means of tubular invaginations. However, in D. Iridis the expanding sporangium encloses a portion of the stipe which helps make up the columella. A more or less concave area above the stipe and in the sporangium is cut off from the rest of the protoplasm. The protoplasm in this cut-off area disintegrates and the area becomes a portion of the columella. From the columella, tubular invaginations push out into the protoplasm and anastomose either with the small vacuoles which are sometimes formed there, or with the invaginations from the peridial wall, or with the peridial wall itself. Invaginations from the peridial wall sometimes connect with the columella. The small vacuoles in Didymium which anastomose with the invaginations are probably responsible for the nodular swellings often found on the mature capillitial threads. Calcium carbonate and other products excreted during maturation of this species are not retained in the capillitium but are transported to the exterior or to the columella.

This work was done in the mycological laboratory of the State University of Iowa under the supervision of Professor G. W. Martin.