The Development of the Ascocarp of Rhizina undulata Fr.

Abstract

1. The mycelium of Rhizina undulata Fr. spreads among the soil particles, and covers the smaller rootlets of pines and other trees, forming a whitish moldlike growth. Upon this subiculum compact masses of hyphae develop as minute, snow white, rounded knobs. These constitute primordia of ascocarps. 2. The ascocarp primordium in the youngest stages shows no evidence of a sexual apparatus. It is made up of undifferentiated hyphae, which at its surface form a palisade layer. 3. The ascocarp is neither at the beginning nor at any subsequent period provided with a hyphal envelope. The fruit body is therefore gymnocarpous and the hymenium is "exposed from the first." 4. There is developed in the interior of the young ascocarp a well defined sexual apparatus from which the ascogenous hyphae arise. The details of the sexual process have been studied and will be described in a later paper. 5. The ascogenous hyphae branch repeatedly and undergo crozier formation in the development of the young asci. The paraphyses are a differentiation of the palisade layer which covers the fruit body at all stages. 7. In the ascocarp of this species there are present paraphysis-like structures which arise early in the history of the fruit body. They are non-septate, thick-walled tubes which originate far down in the hypothecium, traverse the hymenium, and discharge a brown, glutinous secretion at their tips. The writer has applied to these the term "setae." 8. At maturity the ascocarp is variable in size and shape. The brown hymenium is bordered by a sterile white margin. 9. There are present on the lower surface of the ascocarp numerous prominent rhizoids.