This group resembles _Vaucheria_ and the other Siphoneæ among the
Algæ.
ORGANS OF NUTRITION. The mycelium is formed of a single cell, often
thread-like and abundantly branched (Fig. 78). Vegetative propagation
by chlamydospores and oidia. Asexual reproduction by endospores
(sometimes _swarmspores_) and conidia. Sexual reproduction by
conjugation of two hyphæ as in the Conjugatæ, or by fertilisation of an
egg-cell in an oogonium. On this account the class of the Phycomycetes
is divided into two sub-classes: ZYGOMYCETES and OOMYCETES.