Fletevcecism. Bo 
Puccinia eriophori Ecidium cineraria Rostrup | 1883 
* Puccinia obscura Ecidium bellidis Plowright | 1884 
* Puccinia schdleriana Aacidium jacobzese Plowright | 1884 
* Puccinia perplexans Ecidium ranunculi-acridis | Plowright | 1884 
Puccinia vulpine Ecidium tanaceti Schroter | 1884 
* Puccinia arenariicola Ecidium centaureze Plowright | 1885 
* Puccinia phalaridis Aécidium ari Plowright | 1885 
+ Melampsora tremulze Czeoma laricis Hartig 1885 
* Gymnosporangium bisep- | Reestelia botryapites Farlow 1885 
tatum 
* Gymnosporangium confu- | Acidium mespili Plowright | 1886 
sum 
Puccinia pollinise &cidium strobilanthis Barclay 1886 
Gymnosporangium calvipes | Roestelia aurantiaca Thaxter | 1886 
Gymnosporangium macro- | Roestelia pyrata Thaxter | 1886 
us 
Crmartiita asclepiadeum | Peridermium acicola Cornu 1887 
* Puccinia extensicola A&cidium asteris Plowright} 1888 
* Melampsora zcidioides Czoma mercurialis Plowright} 1888 
* Puccinia paludosa Aicidium pedicularis Plowright | 1888 
* Puccinia persistens fEcidium thalictri-flavi Plowright | 1888 
* Puccinia trailii fEcidium acetosze Plowright | 1888 
* is affixed to those species which I have personally investigated. 
+ to those of which I have repeated the cultures, but am not able to confirm 
the above statements. 
The question naturally presents itself to us, Why are 
some species hetercecious and others not? 
One reason is 
pretty obvious, namely, that those Puccinie and Uromyces 
which are hetercecious occur upon host-plants whose cuticle 
is, if not silicous, at least very hard and difficult for the germ- 
tube of the promycelial spore to pierce—namely, on grasses, 
Carices and Junci. This, however, can hardly be the only 
reason, since Schroter has produced the A‘cidium on 
Euphorbia cyparissias from Uromyces pist ; in this case both 
the host-plants have soft epidermal cells. The Coleosporia 
and Melampsore afford similar instances. Whatever may 
have been the cause or causes in bygone ages, the fact is 
that at the present time so completely have these parasites 
become hetercecismal in habit, that the most profuse appli- 
cation of their promycelial spores to the graminaceous host 
is always without result. 
