546 



RESEARCHES ON FUNGI 



pores.^ It is interesting to note the close similarity in appearance 

 between certain pollen grains and uredospores. Thus the pollen 

 grains of the Passion Flower, Passiflora kermesiim, and the uredospores 

 of Puccinia Chondrillae are almost exactly alike in the size and posi- 

 tion of their three pores. ^ Pollen grains, before germinating success- 

 fully, must be deposited upon the surface of a stigma ; and uredo- 

 spores, before germinating successfully, 

 must be deposited upon the epidermis of 

 some host-plant. Thus, both in pollen 

 grains and in uredospores, germination 

 must take place in such a way that a germ- 

 tube shall penetrate the tissues upon which 

 the pollen grains or uredospores happen to 

 lie. The problem of germination under 

 conditions of unilateral attachment has 

 been solved in the same manner by both 

 pollen grains and uredospores, i.e. several 

 or many pores scattered in the cell-walls 

 have been provided ; and this enables the 

 germinating cells to send out their germ- 

 tubes in the most favourable directions 

 relatively to the tissues to be penetrated 

 and thus to economise their food stores and 

 growth energy. 



In teleutospores the rule is, as we have 

 seen, that each cell has one pore only. But 

 teleutospores, with but few exceptions, are 

 not organs of dissemination but probasidia which germinate in their 

 place of origin and not upon the epidermis of a host-plant. Each 

 cell of a teleutospore produces a basidium which grows outwards 

 from the teleutospore-sorus ; and, to provide for the emission of 

 the basidium, only one pore is necessary. The position of this 

 pore is probably about the best possible, if the compactness of the 

 teleutospore-sorus, the relative positions of adjacent teleutospores, 



^ Kerner and Oliver, Natural History of Plants, vol. ii, p. 98, Fig. 217. 

 2 Cf. Kerner and Oliver, toe. cit., Fig. 217, p. 98, and W. B. Grove, loc. cit., 

 Fig. 104, p. 152. 



Fig. 222. — Puccinia Phrag- 

 mitis. a, sori on leaf of 

 Phragmites communis ; b, 

 two teleutospores, with 

 smooth walls, one germ- 

 pore in each cell, and the 

 germ-pore in the highest 

 possible position in each 

 cell ; c, a rough-coated 

 uredospore with 4 equa- 

 torial germ-pores. From 

 W. B. Grove's British Bust 

 Fungi, a, natural size ; 

 b, and c, magnification, 

 600. 



