WING£, CYTOLOG. STUDIES IX THE PLASMODIOPHORACE.I. 17 



As regards the habit of the infection it must be men- 

 tioned that tubers are formed on the host-plant of up to 

 7X3 mm. in diameter (as a rule, however, smaller). These 

 tubers are most often globular and occur as well on the 

 primarj^ axis as more especially, on the secondary ones, which 

 are often by the fungus converted into globular formations 

 attaining the size of a couple of mm. (fig. 9 and 10). The 

 spores are formed in cakes consisting of two layers (fig. 63) 

 inside the stalks, only epidermis and the outermost cortical 

 tissue are not infected. The normally centrally placed vas- 

 cular bundles are displaced and lie scattered about in the 

 deformed stalk — or they are totally destroyed. In case 

 the inner cortical cells contain the fungus they grow to an 

 abnormal size — up to 150 a in diam. and then — as a rule 

 — at the maturity of the fungus they contain more than 

 10 spore-aggregations. In a single host-cell may at the same 

 time be found young myxamoebae and fully mature spore- 

 aggregations. The spore-places vary greatly in size, they may 

 contain over 200 spores consequently 100 in each layer and 

 in such case they attain a size of up to 65 X 45 u.. The 

 nucleus of an infected cell of Calliiriche is often ver}^ like a 

 young amoeba of Sorodiscus (fig. 64). 



The similarity between Sorodiscus and Sorosphaera is as 

 formerly mentioned great, so great in fact, that it would 

 seem most reasonable to unite them into one genus. As, 

 however, the position of the spores at the maturity are con- 

 sidered of great importance for the definition of the genera 

 of this family we shall adopt Lagerheim's »nomen nudum» 

 Sorodiscus, since the spores, as mentioned above, arrange 

 themselves in spore- cakes two layers thick, or one might 

 say — perfectly flattened hollow spheres or hollow ellipsoids. 

 Only occasionally a small lumen may be seen between the 

 two layers of spores, and but rarely the spore-aggregations 

 assume the form of a hollow sphere. 



The Cytology of Sorodiscus. 



As regards this species we are unfortunately unable to 

 state — as is also the case with Sorosphaera Veronicae — 

 how the host-plant becomes infected and we are likewise 



Arkiv för botanik. Band 12. X:o 9. 2 



