1903.] NATURAL SCIENCES OF PHILADELPHIA. 357 



be a fungus similar to Nageli's Schinzia. A paper by Gravis led him 

 to modify his views by ascribing the galls to the combined action of a 

 myxomycete similar in appearance to his Plasmodiophora hrassicce 

 and a fungous mycelium. Moller^^ claimed that the galls were due to 

 a slime mould. Warming^^ attributed the formation of the mycodo- 

 matia to a shme mould allied to the genus Plasmodiophora. Brun- 

 chorst," by his excellent observations, set the matter straight by attribu- 

 ting the galls to a filamentous fungus and estabhshed the genus Frankia 

 for it. Woronin, Frank/^ Sorauer^^ represented several so-called spo- 

 rangia in the cells of the several hosts studied attached to single 

 threads of the mycelium. Brunchorst attempted to prove the fallacy 

 of the observations of these workers by showing that by an optical 

 illusion the sporangia which appear attached in reality lie over the 

 fungous hyphse. Atkinson^^ figures and describes the myceUum and 

 sporangia of a filamentous fungus which he called Frankia ceanothi, 

 because the parasite lived in the roots of the New Jersey tea, Ceanothus 

 americanus. With this contradictory evidence a more careful micro- 

 scopic examination of the mycodomatia is necessary. 



Sections were made of the branches of mycodomatia by first boiUng 

 the dried specimens and then treating them with thirty-five per cent, 

 alcohol to remove part of the air. Transverse and longitudinal sec- 

 tions were made of the dichotomously branched root-like galls. The 

 general microscopic structure of one of these mycodomatial sweUings 

 resembles that of a root (PI. XVII, fig. 1). The center of the section is 

 occupied by the cylinder of wood or xylem, which, however, lacks the 

 larger open elements of the wood of a normal root. The tracheids, 

 irregular in shape and much reduced in size, are compacted together 

 and the medullary rays are displaced out of their true radial position, 

 taking a somewhat sinuous instead of a straight course (PI. XVII, fig. 1). 

 Both in the normal and in the fungous-infested tissues, the medullary 

 ray cells have contents of a rich brown color. External to the wood 

 comes the cambium, theoretically of a single layer of cells, and outside 

 of this the soft bast which consists of rounded cells. In such roots, 

 where the elements have shifted normally from a radial jDosition, the 

 cortex and soft bast are confluent, both in the normal and in the fun- 



^- MOLLER, loc. Cit. 



13 Warming, " Wurzelknollchen bei den Elseagnen," Just's Botanischer Jahres- 

 bericht, 1876, IV a, p. 439. 



1* Brunchorst, "Ueber die Knollchen an den Wurzeln von Alnus und den 

 Elseagnaceen," Botanisches Centralblatt, XXIV, 1885, p. 222. 



'^ Frank, "Krankheiten der Pflanzen," p. 647. 

 / ^® SoRATJER, "Pflanzenkrankheiten." 



1' Atkinson, loc. cit. 



