SECT. I 



CRYPTOGAMS 



409 



being united in pairs. Each telentospore is provided with one germ-pore and on 

 germination in the succeeding year the cycle is Ijeguu 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 {^^). 



In heteroecious species the true relation of the various types of spore can only 

 be made out by means of culture experiments. So long as the connection of the 

 ditTereut forms was not known it was customary to designate each by a special 

 generic name — the Uredo-forms as Uredo ; the aecidia according to their structure 

 as Aecidmm, Roestelia, Peridermium, etc. The generic name is now determined by 



Sir^ 



Fio. 342. — Phragmidium speciosum. A, the first rudiment of an aecidium beneatli the epidermis of 

 a leaf of Rosa ; B, 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 aecidiospore mother-cell ; F, 

 chain of aecidiospores (aj, a.i) separated by intercalary cells (zi, z^ ; sm, the last-formed sporc- 

 mother-coll still undivided. (After Christman.) 



the character of the teleutospores, since they exhibit the most characteristic 

 distinctions. 



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

 graminis. Rust-fungi which produce all the forms of spore are termed eu-forms ; 

 those without euredospores, opsis-forras ; those without aecidia, brachy-forms ; those 

 without aecidia and uredospores, micro-forms ; and lastly, those Avithout aecidia, 

 spermogonia, and uredospores, but with repeated formation of teleutospores before 

 basidia are formed, are termed lepto-forms. 



In those Uredineae which no longer possess aecidia and spermogonia, the cells of 

 the vegetative mycelium arising from the basidiospore are uninucleate, but subse- 

 quently, before the formation of the teleutospores, binucleate cells are found. The 

 binucleate condition is attained, as has already been shown, for several species, in 

 the preparation for the development of the first uredospores or, when these are 

 wanting, for the first teleutospores. It results from the conjugation of two cells, 

 as has already been described for the developing aecidium. This supports the 

 homology of the three kinds of spore. 



Order 3. Auricularieae 

 The basidia, as in the case of the Uredineae, are transversely septate, with four 



