Ui^edospores. 



branches is destined to produce a urcdospore. At first 

 they are of uniform diameter, but soon the upper end 

 dilates so as to become club-shaped (Plate III. Figs. 2, 

 5). Into this dilated extremity the protoplasmic contents 

 of the hyphae are gradually emptied ; and thus by their 

 continued accumulation it becomes almost spherical. This 

 dilated tube-end is now full of granular protoplasm, towards 

 the centre of which appear a few orange granules (in the 

 orange-spored species), while externally it becomes in- 

 vested with a thin cell-wall of its own (Plate III. Fig. 3). 

 The cell increases in size, its walls in thickness, and its 

 contents become more and more distinctly coloured. The 

 orange granules, which consist of reddish-yellow, oleaginous 

 particles, are at first confined to the centre of the cell, 

 and gradually increase in number from the centre out- 

 wards ; so that we frequently observe immature spores, 

 which are orange only in their centre, having the centre 

 surrounded by a hyaline zone. The spore has at this 

 stage of its development two coats — the outer, which is 

 extremely thin and is the dilated mycelial hypha ; and the 

 inner, the proper wall of the spore. The latter increases 

 somewhat in thickness, although it always constitutes a 

 comparatively thin investment. These two coatings 

 become closely applied to one another. The exospore, 

 which is at first smooth, becomes, in most species at their 

 maturity, variously roughened by the appearance of minute 

 projections from its surface (Plate III. Fig. 4). These may 

 be in the form of short, fine spines, when the spore is said 

 to be finely echinulate, or the prominences may be shorter 

 and less acutely pointed (verrucose). De Bary has shown 

 that the spores of many of the Uredinese owe their rough- 

 ness to minute, densely crowded, prismatic, stafif-like pro- 

 cesses, between which similar smaller processes are closely 

 packed. The irregularities of the exospore disappear under 



