Fungi imperfecti, hyphomycetes. Conidiophores are straight, solitary, simple or rarely branched at the base, more or less similar to those of Cylindrocladium (type C. scoparium Morgan), but their filaments, which bear a terminal vesicle, are not multiseptate and never branched and the primary and secondary branches of the conidiophores are more or less parallel; the phialides are more or less divergent or parallel and sometimes show an inconspicuous collarette. Conidia are hyaline, cylindric, smooth, rounded at both ends or slightly pointed at the base, 0-1-septate, and accumulate in a slimy head 50-150 µm in diam.

Fungi imperfecti, hyphomycetes. Conidiophora erecta, solitaria, simplices vel raro ad basim ramosa, plus minusve sicut Cylindrocladium (Typus C. scoparium Morgan) sed filamentis vesiculum terminalem ferentibus non multiseptatis, nunquam ramosis, ramulis conidiophororum primariis et secundariis plus minusve parallelis; phialidibus subdivergentibus vel parallelis, interdum strophium inconspicuum habentibus. Conidia hyalina, cylindrica, laevia, utrinque rotundata vel ad basim leviter attenuata, 0-1-septata, in capitulum mucosum 50-150 µm diam. congregantia.

The anamorph
It would appear that there are further differences between these two genera. Their conidiophores have a different branching pattern. In Cylindrocladium the metulae are more or less curved, occur in (2-)3(-6) series and the branching is often inequilateral, on one side of the stalk of the conidiophore. The filament with vesicle is often referred to as being a sterile appendage but Morrison and French (1969) reported that the vesicles of C. scoparium and C. floridanum Sobers et Seymour could produce mycelium and illustrated a vesicle of C. scoparium producing phialides. Furthermore the appendage is in reality the continuation of the main axis of the conidiophore. Secondary filaments with vesicles can arise from any of the filament cells and also from the conidiophore cells situated below the first metulae and from the metulae as illustrated by Morrison and French (1969) for C. floridanum. The appendage rarely forms part of the sporogenous head, which produces conidia in a palisade layer, but is often found to one side as illustrated by Fawcett and Klotz (1937) for C. citri (Fawcett et Klotz) Boedijn et Reitsma (Figs. 15 and 16).
In Cylindrocladiella the branching of the conidiophores is more compact and symmetrical. The metulae are not curved and usually they occur in two series only. A whorl of metulae and phialides surrounds the base of the appendage. The appendage is never branched and is usually situated in the centre of the sporogenous head, which produces conidia in a ball. Frequently the appendage appears to be placed upon a cell which corresponds in appearance and position with an elongated phialide (Fig. 17). The vesicle can become septate and develop into chlamydospores or it produces apically a new vesicle or a new conidiophore.
In Cylindrocladium the ends of the conidia are bluntly and symmetrically rounded and frequently the lower half of the conidum is distinctly narrower than the upper half, as reported by Morgan (1892). In Cylindrocladiella, however, the conidia are shorter and narrower; the end of the lower half is occasionally slightly pointed and both halves appear to have the same diameter.
There are also differences in cultural characteristics, chlamydospores, (Figs. 13 and 14) and microsclerotia. Boedijn and Reitsma (1950) studied six large-spored species and mentioned the conspicuous white margins of the otherwise strongly pigmented cultures. This contrast does not occur in species of Cylindrocladiella because on most media their pigmentation, which ranges from white to tawny yellow and rarely dark sienna, is less intense and often the transition from the pigmented centre to the white margin is gradual. Furthermore in Cylindrocladiella the chlamydospores are more uniform in size, their configuration is more simple, and often they are produced singly or in unbranched chains. The production of microsclerotia is extremely rare in culture and only known for C. peruviana (Batista et al. 1965), whereas in Cylindrocladium microsclerotia are commonly produced.

Species typica Cylindrocladiella parva (P.J. Anderson), comb. nov. = Cylindrocladium parvum P. J. Anderson in Bull. Massey Agric. Exp. Stn. 183: 37. 1919.