Jan. 27,1923 
Production of Conidia in Philippine Sclerosporas 263 
characterizes the breeze-borne basidiospores of the Hymenomycetes and 
slightly larger than that of the wind-carried oidia of the oak mildew, is 
relatively small, being far less than that of the air-distributed spores of 
Lycopodium, or of the pollen of anemophilous conifers and grasses. 
From its dimensions the volume of an average Sclerospora conidium may 
be calculated roughly as follows: If the spore is regarded as consisting of 
a cylindrical main portion with hemispherical ends, as is diagrammati- 
cally shown in figure 2, the total volume in cubic /x will equal the volume 
of this cylinder plus that of the two hemispheres. In Sclerospora philips 
pinensis , the most commonly encountered length is 33 to 35 /z (34 ju), 
the most frequent diameter 17 to 19/* (1 8 jjl); while the greatest length 
is 52 fx, and the greatest diameter 24 /x. On the basis of these measure¬ 
ments we may calculate the most commonly encountered volume as 
7,125.15 cu. ix (0.000,000,007,125 cc.), while the greatest volume is sim¬ 
ilarly found to be 19,905.18 cu. /z (0.000,000,019,905 cc.). In like man¬ 
ner, in S. spontanea , the most commonly encountered length is 42 /x and 
the diameter is 16 /z, while the greatest length is 64 jx and the greatest 
diameter 20 fx t giving a most common volume of 7,372.29 cu. fx (0.000,000,- 
007,372 cc.), and a greatest volume of 18,011.84 
cu. fx (0.000,000,018,011 cc.). 
The specific gravity of the conidia was not 
determined. It was observed, however, that 
the spores, although they occasionally float, 
usually sink very gradually in a water mount. 
It may probably be assumed without serious 
error that their specific gravity is little if any 
greater than that of the heaviest Hymenomy- 
cete spores (C opr inns plicaiilis, 1.43) studied by 
Buller (2). Their weight, therefore, is rela¬ 
tively very small. 
The rate of fall of the Sclerospora conidia 
was not determined. The fall of these conidia, 
because of their larger size, would undoubtedly be faster than the ve¬ 
locity of 0.429 cm. a second, found by Buller for Coprinus; but it would 
not, in all probability, exceed markedly the 1.76 cm. a second deter¬ 
mined by Zeleny and McKeehan (26) for Lycopodium spores which 
have a specific gravity of 1.175 and a diameter of 31.6 /z. Furthermore, 
because Buller found that the elongate spores of Polyporus squamosus 
when falling soon assumed a position with the long axis horizontal and 
thus were retarded by the increased air resistance, it is probable that the 
similarly shaped Sclerospora conidia, even though larger, behave in like 
manner. In any case it seems justifiable to assume that the rate of 
fall of the conidia is sufficiently slow to facilitate their being carried by 
breezes of even slight strength. Judging from the foregoing, conidia, 
even in absolutely still air, when shed from the upper leaves of maize 
plants at a height of 1.76 meters would require nearly three minutes (176 
seconds) to reach the ground, and that from a height of 3.52 meters, 
which is not infrequently attained by conidiophore-bearing tassels and 
topmost leaves of large maize varieties, the conidia would take but little 
less than six minutes to complete their fall. 
Moreover, Schmidt (21) shows that widespread distribution of a large 
proportion of liberated spores is accomplished by winds of low velocity. 
He calculates that Lycopodium spores which have a rate of fall of 1.76 
cm. a second, when liberated in a wind blowing 36 kilometers (22.5 miles) 
Ir*——1- 
VH r £6m> 
Fig. 2.—Diagrams representing 
Sclerospora spontanea conidia of 
the most common and of the 
largest size schematized to facili¬ 
tate calculation of approximate 
volumes. 
