rUKIUNKAE. 329 



sporidia on germination iiivr infectin-. mycelial hyph In 



the case of r<//< ////////<, the promycelium is formed in-ide the 

 teleutospore in a manner similar to the Protobasidiomycetes. 



I '."-ides teleutospores, there occur uredosporea These are 

 given (ill' from patches or sun throughout the summer till 

 autumn, when they are followed by teleutospores on the same 

 sori. The uredo^pore< somewhat resemble the teleutospores, 

 luit pen,. rally consist of one cell only with a thinner coat of 

 lighter colour; they either germinate at once without a 

 period, and -ive rise to a ^Tin-tube capable of direct inl'e 

 of new hosts; or less frequently they are restful-spores for 

 a time. 



A third form of spore occurring in the life-history of the 

 1 redineae is the aecidiospore, produced in a special structure, 

 the aecidium. The aeeidium is developed inside the leaves or 

 other organs of the host-plant, and when mature ruptures the 

 overly in- epidermis; it has as a basis a firm hyphal tissue, 

 the upper surface of which becomes a disc of short erect sporo- 

 phores. From each sporophore there is formed hy intercalary 

 -lowth a chain of cells consisting alternately of spores and 

 -mailer intermediate cells, which do not become spores. The 

 youngest cells in an aeeidium are those next the spMn.phnre- 

 dise, and they are forced outwards by intercalation ,,f younger 

 cells between them and the disc. The cells so produced 

 become alternately intermediate cells and spores; the 1'orm.T 

 increase for a time, then decrease and disappear, the spores 

 however continue to inerea-e j), si/e as tin- chain -rows forward 

 and to take on the character.^ of the mature aecidiospore till 

 they are tinally shed from the aeeidium. The production and 

 distribution of aecidiospores may thus go on continuously for 

 a considerable time. The .-porophoivs at the periphery of ihc 

 disc do not however pn-diiee spores; chains of cells are also 

 produced from them by iniei<-alar\ -ro\\th, but the cells are of 

 equal si/e, and remain closely connected with their nei-hbom -, 

 30 as to form a membranous coverin- over the spore-.-orus, 



thi> i> the >o-callei| pel'idilim, oil ruptllle of which the aecidjo- 



Bpon ipe. In many I'redineae the peridium is .siippiv-> M -d 



(CaeOmO)] ill othel-s (/'///-"//////'///'///I it is leplaced by other 

 Structures, the ]iaraphy<e-. The BpOrOS of the -einis k'/n/njJti/f/ii/tt 

 are produced in series in aecidia cnclo-ed by a peridium, but in 



