Cylindrical to slightly flared. Beyond the region of attachment to the spore, only a single layer continuous with L1 of the spore wall constitutes the hyphal wall. L2 of the spore wall stops abruptly in the region of attachment and thus is not part of the more distant hyphal wall structure. On a slide with 56 spores, only two showed the detail described above for the subtending hypha. The photos below are biased toward the most darkly staining regions for clarity in showing structures, so they are not representative of the full range of variation.
Vesicles tend to stain darker than arbuscules or intraradical hyphae when present.
These features were redescribed by Kennedy et al. While these two species are similar, they can be readily distinguished with a practiced eye. The type species fits in the latter group, but we actually have more isolates of the former in monospecific pot cultures. In our experience, G. spurcum initially is fairly aggressive when cultured alone or together with other species, but tends to become attenuated after several successive culture generations. A new endomycorrhizal fungus from Arizona.