SPORE-WALL PORES 



547 



etc., be taken into account. Thus, in Puccinia graminis (Fig. 204, 

 p. 505) and P. Phragmitis (Fig. 222), the upper cell of the teleuto- 

 spore has a terminal pore and the lower cell a pore as near to the 

 dividing wall as possible ; and it is obvious that these pore-positions 

 facilitate the emergence of the germ-tubes into the outer air. The 

 teleutospore and the uredosporeof P. graminis and of other Uredineae 

 have different problems to solve in their germination, and the differ- 

 ence in the number and position of their pores is an expression of 

 their adaptation to carry out their special functions. 



Among Pucciniae, other than Puccinia graminis and P. Phrag- 

 mitis, having the pore of the lower cell 

 of the teleutospore at the highest 

 possible point are : P. punctata on 

 Galium, P. Buxi on Buxus, P. Malva- 

 cearum on Malva, etc., P. Calthae on 

 Caltha, and P. Lychnidearum on 

 Lychnis.^ But there are a number 

 of exceptions to this rule, e.g. 

 Puccinia Vincae on Vinca (Fig. 223, 

 a, b), P. Taraxaci on Taraxacum, 

 P. major on Crepis, P. Primulae on 

 Primula, and P. Pimpinellae on 

 Pimpinella.2 Whether or not there 

 is any biological advantage in the pores in these Pucciniae being 

 situated low down in the cell-walls remains to be investigated. 



Why should the teleutospores of many species of Phragmidium 

 differ from those of Uromyces and Puccinia in having three pores 

 in each cell instead of one ? I am uncertain what is the correct 

 answer to this question. The teleutospore of a Phragmidium is 

 composed of a row of cells and each cell produces a short curved 

 lateral basidium, so that several basidia may be produced by a 

 single teleutospore at one time. It is possible that the cells of a 

 teleutospore, when germinating, mutually influence one another 



Fig. 223. — Puccinia Vincae. a, a 

 teleutospore, seen dry, with the 

 germ-pore of the lower cell near 

 the pedicel ; 6, the same, seen 

 wet ; c, a uredospore, aculeate, 

 having 3 germ-pores. From 

 W. B. Grove's British Rust 

 Fungi. Magnification, 600. 



^ For illustrations vide W. B. Grove, The British Rust Fungi, Cambridge, 1913, 

 Figs. 115 (p. 165), 153 (p. 206), 154 (p. 207), 165 (p. 216), and 168 (p. 219). 



2 For illustrations vide W. B. Grove, ibid.. Figs. 106 (p. 154), 109 (p. 158), 

 127 (p. 177), 129 (p. 180), and 136 (p. 188). 



