GROUP I. THALLOPHYTA : FUNGI : ^CIDIOMYCETES. 



307 



copsis, such as Uromyces Behenis, U. Scrophularice ; species of Pucciniopsis, 

 such as Puccinia Bcrberidi*, P. Liliacearum, P. Tragopogi; species of Phrag- 

 midiopsis, such as Xenodochus carbonarius) . In some of the foregoing cases 

 the mycelium may bear a few uredogonidia ; in Phragmidium uredogonidia 

 are always formed. 



It is not, however, always the case that when there are distinct Uredo- and 

 JEcidium-forms, these are heteroecious ; they frequently inhabit the same host- 

 plant, that is, they are autcecious (e.g. species of Auteu-uromyces, such as 

 Uromyces Fabcc, U. Orobi, U. Trifolii, etc. ; species of Auteupuccinia, such as 

 Puccinia Galii, P. Asparagi, P. Calthce, etc.) When there are not distinct 

 Uredo- and ^Ecidium-forms the fungus can only be autoecious. 



The reproductive organs and cells, as described above, present certain variations 

 by which the different genera are distinguished. Thus, in Endophyllum, the 

 group (sorus) of teleutogouidia is invested by a definite wall ; in Gymnosporan- 

 gium and 

 Cronartium, 

 the teleuto- 

 g o n i d i o- 

 phores form 

 a projecting 

 column 

 which, in 

 Gymnospor- 

 angium, is 

 gelatinous. 

 In Coleo- 

 sporium tbe 

 promycel- 

 ium is uni- 

 cellular 

 (Fig. 215 C), 

 whereas in 

 all other 

 forms it is 

 multicellu- 

 lar; in this 



genus also several uredogonidia are formed successively from the samo goni- 

 diophore. The primitive teleutogonidium undergoes no division, so that only 

 one is found on each gonidiophore, as in Uromyces ; or it divides transversely 

 once to form two gonidia, as in Puccinia ; or several times, to form a ro~/ of 

 gonidia, as in Phragmidium ; or obliquely, to form a group of three gonidia, 

 as in Triphragmium. The groups (sori) of uredogonidia are sometimes in- 

 vested by a wall, as in Cronartium. In Phragmidium the wall of the fficidium 

 differs from that of the other forms in that it does not consist of a definite 

 layer of cells, but is represented by a number of club-shaped unicellular hairs. 



In most cases the teleutogonidium is a resting-gonidium ; but in some forms, 

 such as Leptouromyces (e.g. Uromyces pallidus, U. Ficarice, U. Croci, etc.), 

 Leptopuccinia (e.g. Puccinia Nalvacearum, P. Buxi, P. Circcece, etc.) Chryso- 



FIG. 217. Chrysomyxa RJiododendri in a leaf of Rhododendron hirsutum: 

 vertical section of a sorus of teleutogonidia ; e epidermis of under surface 

 of the leaf; t terminal teleutogonidia beginning to germinate; to the left 

 a teleutogonidium has germinated, giving rise to apromycelium (pr) with 

 sporidium (sp) borne on a sterigma st. (x 140 : after de Bary.) 



