CRYPTOGAMS 



407 



vulgans). In the spring the hibernating double teleutospores give rise to 

 transversely septate basidia, from which the four basidiospores are abstricted 

 (Fig. 348, 2). These are scattered by the wind, and if they fall on the leaves of 

 the Barberry they germinate at once. The germ-tube penetrates the cuticle, and 

 there forms a mycelium which gives rise to spermogonia on the upper side of the 

 leaf, and to fecidia on the under side (Fig. 350). This form of the fungus is 

 known as Ai'dilium Berberidis. On the rupture of the peridium the reddish- 

 yellow fecidiospores are conveyed by the wind to the haulms and leaves of grasses, 

 upon which alone they can germinate. The mycelium thus developed produces 

 at first uredospores (Fig. 348, 5). They are unicellular, studded with warty 

 protuberances, and provided with four equatorially disposed germ-pores. In 

 of the reddish-yellow fat globules contained in the protoplasm of 



C 



FII;. :;">-. I'liriiiiiitliliniii *iir,-i<>xi<ni. A, The first rudiment of an a-cidimn beneath the epidermis of 

 a leaf of Rosa ; R, the division of the end-cell of a hypha into the upper, transitory, sterile cell 

 and the lower fertile cell ; C, conjugation of two adjoining fertile cells ; D, later stage in which 

 the first nuclear division is completed ; E, abstriction of the first fecidiospore mother-cell ; F, 

 chain of svcidiospores (a^ 2 ) separated by intercalary cells (Z], z) ; sm, the last-formed spore- 

 MKither-cell still undivided. (After CHRISTMAS.) 



the spores, the fructification forms red markings (formerly termed Uredo lincaris) 

 cm the epidermis of the host plant. The uredospores are capable of germinating 

 at once on the wheat, and thus the rust disease is quickly spread. Towards the 

 end of the summer the same mycelium produces the dark brown, thick-walled 

 teleutospores, which in this species are always double, being united in pairs. 

 Each teleutospore is provided with one germ-pore, and on germination in the 

 succeeding year the cycle is begun afresh. The mycelium of the Uredo form may 

 hibernate in winter wheat, and thus the rust may appear in the spring without 

 the previous formation of basidiospores or of aecidia. 



Other common Rusts on grasses or cereals which are closely related to Puccinia 

 graminis are Puccinia dispersa on the Rye, which develops its secidia on Anchusa, 

 and P. triticina and P. <jhi miirvii), which occur respectively on. Wheat and on 

 \Vlicat, Rye and Barley. The a?cidia of these latter forms are unknown. 



All Uredineae do not exhibit so complicated a course of development as Puccinia 



iirn nt iii is. Certain species produce only basidia from germinating teleutospores, 



'or, in addition to teleutospores, only uredospores which are developed on the same 



2 D 2 



