North Island: WKR, Yakas Tree Track, 24.vi.81, coll. EH, no. 43685 (TENN); WKR, vic. Forestry Headquarters, 25.vi.81, coll. RHP, no. 43686 (holotype, PDD; isotype, TENN); Auckland, Titirangi, footpath, 29.vi.81, coll. J. M. Dingley &RHP, no. 43677 (TENN); WKR, Te Matua Ngahere track, 31.v.82, coll. RHP, no. 43552 (TENN); PSF, 2.vi.82, coll. GS, no. 43607 (TENN).

Fruit bodies up to 90 x 4 mm, simple clubs occurring singly or in small groups of up to 12 individuals arising from individual or common small white mycelial patches, very narrowly fusiform to narrowly cylindrical, somewhat sinuate. Club off-white when young, in age buffy ("cartridge-buff"), pale greenish grey ("deep olive-buff" mostly, upward to "pale olive-buff" or "olive-buff") to dull greenish yellow ("colonial buff"), appearing waxy; apex narrowly rounded, often somewhat darker than club (in age?). Stipe white when young, then concolourous with club ("deep olive-buff") or yellower ("mustard-yellow"), minutely shiny-silky. Taste and odour negligible.
Tramal hyphae hardly inflated, clampless. Subhymenium well-developed, pseudo-parenchymatous. Basidia 40-50 x 8-10 µm, bifurcate to clamped; contents homogeneous to multiguttulate (guttules highly refringent); sterigmata 4, slender, erect.
Spores (fig. 24) 7.2-9.0 x 6.5-9.0 µm (E = 1.00-1.16; E^m = 1.07; L^m= 7.88 µm), globose to subglobose, smooth to echinate, thin-walled; contents multiguttulate in youth, uniguttulate by maturity, the guttule highly refringent and obscuring observation of the spore wall; hilar appendix stout, papillate-truncate; ornamentation of narrowly conical to cylindrical spines up to 2 µm long.

Under kauri (Agathis australis) forest.

Receptacula ad 90 x 4 mm, simplicia, gregaria vel caespitosa, juniora alba, vetustiora pallide isabellina. Hyphis efibulatis; basidiis fibulatis. Sporis echinulatis, ut in oratione infra.

Only very careful observation will reveal the spiny spore wall, and this character would seem to be the only one to separate Clavaria echino-olivacea from C. subsordida, with smooth spores but virtually identical fruit bodies and micromorphology. Indeed, the latter may be conspecific, but I have found no spiny spores.
Corner (1950; p. 238, footnote) found spiny spores in spirit-preserved material of Clavaria gibbsiae var. tenuis t. micropora but dismissed them as contaminants. All other characters match well, so I accept those spores as belonging to the fungus in question. Corner did not know pale-coloured Clavaria taxa with spiny spores, and with the caveat repeatedly presented here (under individual spiny-spored taxa) it is easy to accept his conclusion.
Ordinarily, nomenclatural recommendations would result in the form being raised to species rank, but the epithet microspora is pre-empted by Clavaria microspora Josserand. Moreover, I have not examined the type of Corner's taxon, and therefore I am reluctant to use it as the type of this taxon. Therefore, I have proposed a new species, with Corner's forma as a synonym.
It is necessary to piece together the original description of Corner's forma, combining the macroscopic data from var. tenuis (Corner 1950; p. 237-238) except for spore data, and forma microspora (Corner 1950; p. 238-239, especially the footnote). I assume that Corner's plate 2 illustrates var. tenuis f. tenuis, not f. microspora.
Clavaria echino-olivacea is similar to C. californica Petersen, which produces similar fruit bodies (white to pale dull yellow; "cartridge-buff") and ellipsoid spores.
Fruit bodies of TENN no. 43686 are brighter yellow than those of others, but micro morphologically they are identical. Fruit body shape and habit (loosely cespitose from individual or common mycelial patches) also match completely. The colour discrepancy may be due to the age of the fruit bodies or to some micro-ecological variation, but I consider the specimens to be contaxic.

Fruit bodies up to 90 x 3 mm, simple clubs, cylindrical, scattered to gregarious, arising from small whitish mycelial patches. Club ivory to pale greenish yellow (off-white to "pale olive-buff"), opaque, appearing waxy; equal to tapering slightly upward; flesh concolourous. Stipe up to 40 x 2 mm, shining-silky, off-white, equal.
Tramal hyphae inflated, long-celled, thin-walled, clampless, parallel, tightly packed, free to adherent; secondary septa common; crystalline material deposited among tramal hyphae. Subhymenium poorly developed, pseudoparenchymatous. Hymenium hardly thickened; basidia (Fig. 35) 30-35 µm long, clavate, narrow and attenuate below, clamped; contents multiguttulate at maturity; sterigmata 2, long, stout, somewhat divergent, straight.
Spores (Fig. 36) 8.6-10.8 x 6.5-7.6 µm (E = 1.19-1.67; E^m = 1.40; L^m = 9.84 µm), subglobose to broadly ellipsoid, smooth, thin-walled; contents opalescent; hilar appendix prominent, broad, papillate.

North Island: WKR, across river from Forestry Headquarters, 24.vi.81, coll. RHP, no. 42411 (holotype, PDD; isotype, TENN), 42428 (TENN); WKR, 24.vi.81, coll. EH, s.n. (ZT); WKR, vic. Forestry Headquarters, 25.vi.81, coll. RHP, no. 43667 (TENN). South Island: FGNP, Rd to Gillespie's Beach, 9.v.82, coll. RHP, no. 43565 (TENN).

On leaf humus and very rotten, soggy wood.

Receptacula ad 90 x 3 mm, simplicia, gregaria, pallide olivacea. Hyphis efibulatis; basidiis fibulatis, 2-sterigmatibus. Sporis subglobosis vel late ellipsoideis, laevibus, ut in oratione infra.

corner (1970) included four taxa with white fruit bodies and broad spores in subg. Holocoryne. None is 2-sterigmate, and I can find no other report of such a fungus in the literature on Pacific taxa.
This and Clavaria subsordida were placed under a single taxonomic designation based on fruit body morphology, for they are extremely similar macroscopically. Closer examination revealed that C. ypsilonidia produced ellipsoid spores and strictly 2-spored basidia, immediately separating it from C. subsordida. Also, both taxa are similar in fruit body colour and stature to C. echino-olivacea, which produces spiny spores. Care must be taken to distinguish these three taxa.
Basidia in Clavaria ypsilonidia are short (not more than 50 µm long by hymenial measurements) and somewhat agglutinated, obscuring the basal loop-like clamp. The basidia of C. subsordida are virtually free (not agglutinated) and the clamp - or bifurcate basidial base - is easily observed.
Fruit bodies of the species vary in colour from virtually pure white (which I originally designated a separate species) to pallid olive-buff, sometimes with the club pigmented but not the stipe. This colour variation appears irregular, however, and unaccompanied by micro morphological variation, so I consider that no separate taxa are warranted.