138 VEGETABLE PAEASTTES. 



sometimes lies embedded in a concept l aculum, borne by the recep- 

 taculum, sometimes not. The spores are generally very small 

 bodies, varying in size, according to the species, from O004-5 

 or some hundredths of a millimetre. Their smallness enables 

 them to penetrate every natural cavity the folds in the skin of 

 animals, cracks in plants, in short everywhere where dust could 

 get ; and, like the latter, they are carried by the wind on to slimy 

 surfaces and deposited there. Their form is generally oval or 

 spherical, sometimes triangular with normal rounded corners, or 

 irregular, and often of a longish oval shape or spindle-like. 

 Their consistency is very great, so much so that they can scarcely 

 be crushed between plates of glass. This firmness facilitates 

 their penetrating the skin. The consistency of spores which are 

 yet between the sporangia is less ; they are found to be fre- 

 quently elastic and pliant, if they are of a longish shape. Spores 

 do not lose their capacity of germinating by drying, if in so 

 doing the temperature is not raised beyond 70 C. (158 Fahr.) 

 They are less dense than water and float on it. Wind and 

 water may therefore spread and carry them far and wide. They 

 vary in colour gray, brown, yellowish, or, if the light is falling 

 on them, almost colourless. In reflected light they look gray, 

 yellowish or of a white, more or less brilliant. If they reflect 

 the light strongly, they show in the centre a brilliant, usually 

 yellowish spot. As long as they lie in the sporangium, however, 

 they are mostly colourless, and look polished, transparent, or 

 greenish. When very numerous they give to the touch the feel- 

 ing of fine sand, their surface has a brilliant appearance, and they 

 sometimes possess a peculiar mouldy odour and taste, especially 

 when they fructify and are free. They are apt to produce inju- 

 rious effects on man when introduced into the body, by way of 

 the food or during respiration. 



Chemical reagents act but little on them. Tincture of iodine, 

 when employed alone, colours them of a dark yellowish-brown, 

 like other purely nitrogenous substances. When their cellulose 

 walls are not coloured blue by the action of the iodine, their 

 nitrogenous contents become brown. On treating them with 

 hydrochloric or nitric acid, or, better still, with hot sulphuric 

 acid, before adding tincture of iodine, the nitrogenous part coagu- 

 lates, contracts, and separates from the sides of the spores, and 

 remains, forming irregular masses in the centre. On applying 

 afterwards tincture of iodine to these parts they become brown, 



