USTILAGO. 301 



belong to the tissue of the Polygonum and may form simple 

 filaments, or several such filaments may become bound together 

 by lateral connections. Each strand becomes surrounded by 

 spores of the Ustilago which are set free on rupture of the 

 fruit-gall, while the cell-strands laterally bound to each other 

 are loosened from the surrounding tissue as the capillitium. 



" The spores germinate in water, producing short unicellular 

 promycelia and fairly large conidia, which coalesce before they 

 germinate. The mycelium is confined to a small part of the 

 stem, twigs, or inflorescences of the host-plant. The hyper- 

 trophied parts of the stem contain abnormal spongy wood, 

 which easily decomposes and brings about the death of the 

 galls, along with parts of the stem situated beyond them, or 

 even the whole plant. The normal production of cambium is 

 completely destroyed in the galls. The pith and primary rind, 

 however, remain uninfluenced. The cambium produces, both 

 outwards and inwards, such a mass of thin-walled parenchyma 

 that the normal bast is forced asunder and disarranged. In 

 this way rupture of the sclerenchyma-layer ensues, whereby the 

 primary rind is destroyed, and the abnormal tissue formed by 

 the cambium emerges to view. It is from such places that 

 the excrescences described have their origin." 



It will be seen we have here the partners of a symbiosis 

 becoming so adapted to each other that the host-plant produces 

 a special tissue for the distribution of the spores. This case 

 goes further than most of those already mentioned in § 5; 

 but the bushes produced by Caeoma deformans for the formation 

 of its spores are again a distinct advance on the " fruit-galls " 

 of this Ustilago. 



Cintractia. 



Spore-masses developed inside a stroma and passing outwards 

 so that the mature black spores lie freely exposed. 



Magnus ' has recently separated Ustilago caricis Pers. and U. suhinclusa 

 Korn., and placed them under this genus, because their spores are developed 

 only in the epidermal cells of the host-ovary. 



Cintractia caricis (Pers.)^ (Britain and U.S. America). The 



^Cornu. AnncU. d. sciences natur., Ser. vi., Vol. xv., 1883. Plate XV. 

 Magnus, Botan. Verein d. Prov. Brandenburg, xxxvii. Brefeld, Schimmelpilz 

 Heft XII., 1895. 



