EICHARDS. DEVELOPMENT OF iECIDIA. 265 



breaking through, the spores and peridium began to form as early as 

 in the other a;cidia. The subsequent develoj^ment was simply a 

 multiplication of the spores and peridial cells. In the species chiefly 

 examined, Rcestelia lacerata on Aiitelanchier Canadensis, there were 

 however some facts made out that should be mentioned. 



The mass of pseudo-parenchyma in the primordium is elongated 

 vertically, and appears still to keep on forming, while the hymenium 

 is developing, until it almost reaches the surface of the tissue in which 

 it lies. Although excellent young material was obtained, it was 

 impossible, owing to the very compact and obscure nature of the 

 primordium and the very small size of the hyphie, to make anything 

 out of the youngest stages even by all the various methods tried. The 

 young basidia are very narrow, and those which form the peridium 

 swell abruptly into the peridial cells, which at first, though large, are 

 very thin-walled. The intercalary production of basidia is more 

 marked here than in any a?cidium previously examined, and owing to 

 this the connection of the peridial cells with the spore chains is rapidly 

 lost. The cells of the peridium, which are at first about the normal 

 shape, lengthen very much, and become of the elongate almost rhom- 

 boidal shape found in the mature a?cidium. 



General Discussion of the ^cidium Stage. 



In comparing the results of the foregoing observations with the 

 accounts of the development of the oecidium already published certain 

 differences of considerable importance will be noticed. As regards 

 the formation of a primordium with a mass of pseudo-parenchymatic 

 cells in the centre, there appears to be a general unanimity of opin- 

 ion, although Neumann* figures the formation of the hymenium at a 

 much earlier stage than seems to be the case in the tecidia described 

 here or in those mentioned in previous accounts. In Plate XVI. 

 Fig. 3 of his paper he shows very definite indications of a hymenium 

 before the appearance of the compact pseudo-parenchyma. The 

 same is true of his figure of the aacidium on Ficaria ranunculoides, 

 but if one may judge from the drawing of the form on Eaphorhia 

 Cyparissias, the condition is more nearly as I have seen it myself, 

 where there is a definite pseudo-parenchyma before the formation of 

 the young basidia. Concerning the formation of the sporogenous 

 hyphse, there seems to be but little better knowledge in the pub- 



* Loc. cit. 



