Abstract
When sown on the surface of distilled water, uredospores of Puccinia coronata Corda begin to swell and then issue projections out of germ-pores. The present paper mainly deals with observations on these morphological changes during the early stage of germination and also describes some distinguishable points between projections and germ-tubes.
The volume of spores becomes about 2 times in approximately 20 seconds after being floated on water drop. Already at this time spores seem to have been physiologically activated and also to have diluted by intake of water their own components contained in high concentration to such a level as having no inhibitory effect for germination process. The rise of volume continues for 20 minutes to reach the maximum-3.3 times the volume of resting spores, and there is a little shrinkage of the original spore with the onset of germ-tube growth. During 8 to 20 minutes of incubation, spores protrude respectively 1 to 6 small projections of “Dome-type”, which are less than 3μ in length. The appearance of projections in questhon is earlier on the half-sphere of a spore in contact with water than on the opposite one, but in their total number there is no difference between both.
One (rarely two) of the projections of a spore changes from “Dome-type” to “Cylinder-type” in 30 to 50 minutes after the first appearance, and it enters into a continuous growth rapidly. The latter type projection differs from the former one not only in a morphological shape but also in the response to air-drying as well as in the sensibility against chemicals. On the basis of these facts the writers considered that “Cylinder-type” projection alone, the length of which is larger than 3μ, should be regarded as a real germ-tube and that “Dome-type” projection would be an intermediate organ growing into a germ-tube.
