DAMPING OFF. 247 



any serious attempt to determine the species. T. W. Galloway 

 from a careful study determined it from seedlings of Cilia, Viscaria 

 Lobelia, etc., in the Botanic Garden of Harvard University. He 

 did not however observe the zoospores. Humphey 14 also carefully 

 determined the species, but does not describe the zoospores. 



DAMPING OF PROTHALLIA. 

 Artotrogus intermedius (deBary). 



This species was first noticed in fern prothallia growing in the 

 botanical conservatories of Cornell University in the month of 

 February, 1894. The affected prothallia were quite soft, limp, and 

 darker in color than the healthy ones. Some were placed in water 

 on a glass slip and kept in a moist chamber. The following day 

 the fungus had grown out of the prothallial tissue and had ex- 

 tended a considerable distance over the slip. The mycelium is at 

 first non setate and contains granular protoplasm which is present 

 in minute irregular masses, having in the larger threads much the 

 appearance of the protoplasm in some mucors, and in some cases 

 well marked and strong currents of the protoplasm have been ob- 

 served, which resemble the movement of the protoplasm in these 

 plants. 



The threads branch monopodially, the extent of the branching 

 depending, to a certain extent on the amount of the vegetive 

 growth. The threads put out in the water from the prothallia 

 may be quite long and possess primary and secondary branches 

 before condia are developed to any great extent. The conidia are 

 developed at the ends of the main threads or their branches, the 

 hypha swelling at the end into a rounded body several times the 



* 8th Ann. Kept. Mass. State Agr. Exp. Station, 220, 1890. 



Explanation of Plate II. Artotrogus intermedius (deBary). 



Figs. 10, n, 12, 13, conidia developed in chains. 



Figs. 14 and 15, conidia borne in a manner resembling the conidial fructi- 

 fication in Phytophthora. 



Figs. 17-23, different stages in the development of the zoospores. 



Fig. 24, free zoospores with a cilium at each pointed end, passing into 

 amoeboid movement and becoming divided into oval unciliated zoospores. 



Fig. 1 6, intercalary conidium. 



All the figures from camera lucida drawings and magnified 50 times more 

 than the scale. Scale i millimeter. 



