PUCCINIA. 331 



tissue, more or less elongated in a direction at right-angles to the 

 surface of the leaf, and, from the small development of its inter- 

 cellular spaces, is essentially distinguished from the spongy 

 parenchyma of the surrounding parts of the leaf. The epidermis 

 of both surfaces of the leaf has not been affected in form. The 

 contents of all these cells are disorganised, and consist partly of 

 colourless oil-drops, partly of greenish-yellow and reddish drops 

 and granular masses, proceeding from the chlorophyll grains and 

 the cytoplasm. The entire tissue of the cushion shows its inter- 

 cellular spaces traversed by delicate, septate, slightly-branched 

 fungal hyphae, containing oil drops. These extend on both sides 

 to the epidermis. With chlorzinc iodine, as also with iodine and 

 sulphuric acid, blue coloration is not induced, since fungal- 

 cellulose rarely shows this reaction. The aecidium-cups, as we 

 have them before us in longitudinal section, are sunk more than 

 half in the tissue of the cushion. We easily determine that the 

 mycelial hyphae under the cups form a dense, almost pseudo- 

 parenchymatous, layer, from which, perpendicularly outwards, 

 and parallel to one another, rise .numerous thicker club-shaped 

 hyphae, without interspaces, forming the so-called hymenium. 

 These hyphae, the basidia, pass over at their ends into straight 

 rows of spores, which at the basidia are colourless, and, from 

 mutual pressure, polygonal, but gradually become orange-red and 

 rounded. Higher up the spores separate from one another, and 

 are evacuated from the opened cup. The observation of the 

 youngest spores upon the basidia convinces us, however, that 

 they are cut off one after another by cross-walls, from the apex of 

 the growing basidia. The unilamellar wall of the fruit (the 

 peridium) consists of cells which look very like the spores, but 

 remain polygonal, and do not separate laterally from one another. 

 Their fine delicately porous walls are especially strongly thickened 

 on the outer side. The developing peridium pushes back and 

 destroys the surrounding tissue of the cushion, and tears open the 

 epidermis in order to open out to the exterior. 



The pear-shaped spermogones, especially found upon the 

 upper side of the leaf, are, like the aecidium fruits, surrounded, 

 though less strongly, by a weft of hyphae, from which arise densely- 

 crowded parallel threads, running towards the middle line of the 

 structure. These threads are very delicate ; those found in the 

 upper part of the organ project as delicate bundles towards the 

 exterior (compare Fig. 118 later). These delicate threads, the 



