SAPROPHYTES AND PARASITES 



which soon fall away. The germi nation of teleutospores 

 results there fore in a p romyceliuni,~ which develops small 

 secoTidary or promyeeliaX &poj£S^nd_these latter are ready to 

 ge rminate at onc e. W hen t hese promycelial spores are placed 

 on the damp surface of the leave s of "Th e Tiost-planlL they 

 germinate, and the growing point enters one of the stomata, 

 whe re it forms a m ycelium , the contents of thlT^romycelial 

 s pore pas sing down the tube, whUsTTthe empty "spbre-case~soon 

 falls away. This new mycelium may produce spermogonia 

 and aecidiospores, thus revertin g to" T he oricnnajpoint, j)f m 

 departure ; or it may give rise to a crop of uredospores, 

 without the intervention of aecidiospores ; or it may pro- 

 duce teleutospores, which are functionally alike or unlike 

 the parental teleutospores from which the promycelium was 

 derived. Through out all these mutations there is nx>diyjer- 

 gence from the endo phytal cnaracter~"6T the parasite, which is 

 of a peculiar and ch aracteris Tic "type. Hefe7 thenTwe have in 

 brief the typical life-history of "one of the Uredineae — the 

 teleutospores in some instances being unicellular, and then 

 Uromyces ; or bicellular, and then Puccinia ; or multiseptate, 

 and then Phragmidium ; the character of the teleutospore 

 determining the generic name to be applied to the cycle. 



There have from time to time been suggestions of hereditary 

 transmission in Uredinous infection, but as the frank accept- 

 ance of such a possibility would weaken the effects of such 

 results as are claimed to follow upon artificial cultivation, the 

 advocates of heteroecism ignore as much as possible all sugges- 

 tions of hereditary transmission. Analogy nevertheless favours 

 the probability of inheritance, and some few stubborn facts 

 seem to support this view. Some years since we had occasion 

 to examine some celery plants, the leaves of which were badly 

 attacked by Puccinia, whilst other plants in the same garden 

 did not show a single diseased leaf. Upon inquiry it was 

 found that the diseased plants were raised from seed which 

 had been derived from plants badly diseased at the time, but 

 that the healthy plants were reared from seed which had been 

 saved from plants without trace of disease, either in the past 

 year or in their progenitors of preceding years. The foliage of 

 all the diseased plants was destroyed, and no disease appeared 



