8 A. Barclay— On a TJredine affecting the [No. 1, 



measurements were on the whole very uniformly maintained. After 

 the spores had been moistened with water for a few minutes, their average 

 length became 44ft and their average breadth 21/^. The epispore is 

 thick, measuring about 2-1/x. Seen in optic section, the epispore appears 

 to be coarsely radially striated, an effect due probably to the overhanging 

 and underlying processes on the surface. The endospore appears to 

 consist of a fine homogeneous membrane, but is ill-defined. The con- 

 tents are finely granular and yellow (fig. 7). 



The spores are given off serially in rows from the hymenium, 

 a small intercalary cell separating successive spores (fig. 8.) Traced 

 from without inwards each successive spore becomes smaller, until at 

 last no distinction can be made between spore and intercalary cell, and 

 these merge gradually into tlie round basidial cells forming the floor of 

 the hymenium. 



The peridium is very resistant and consists of two layers of cells 

 which are considerably larger than the spores (fig. 16). 



(c) Microscopic Characters of the Uredinal Fungus.— The general dis- 

 tribution of the mycelium in the tissue of the needle is shown in figs. 23 

 and 25, which represent transverse sections. Masses of mycelial filaments 

 occur between the cells of the parenchymatous tissue. The dislocation 

 of the cells by the mycelium is much more uniform and symmetrical than 

 in the case of the secidial affection, where special aggregations are apt to 

 occur at certain places. The filaments in this form are also much more 

 convoluted. Both in transverse and longitudinal sections the masses of 

 mycelium present the appearance of confused more or less circular out- 

 lines resembling a pseudoparenchyma. This appearance is due to the 

 extreme convolution of the filaments and to their frequent branchmg 

 (fig. 14). The majority of the hyphae have a greater diameter than 

 those of the secidial form ; but they vary in this respect greatly. Most 

 of the hyph^ measure about 8/x in breadth, but some are to be seen of 

 half that size (fig. 13, a Sf h.) _ , 



In this form, as in the last, the great mass of the mycehum is con- 

 fined to the parenchymatous tissue. The arrest of the filaments at the 

 sheath enclosing the central wood bundle is very abrupt, more so even 

 than in the secidial form, for the continuity of the cells is scarcely at all 

 broken (fig. 25). Some filaments, however, do pass through and may 

 be traced both between the parenchymatous cells and to a lesser extent 

 within the phloem. In this form, also, the central sclerenchyma cells are 

 replaced by a mass of convoluted mycelium. In every transverse section, 

 the single large empty cell noted in the description of the normal needle 

 may be seen between this mass of mycelium and the phloem. Elsewhere 

 within the central bundle, the hyphae are less numerous and arranged 



