274 Journal of Agricultural Research voi. iv, no. 3 



OBSERVATIONS ON SPORE GERMINATION 



The germination of the spores in the base of the old sorus has already 

 been described. The writer has also studied their behavior in culture 

 media. One of the first problems undertaken in this study of 5. suh- 

 terranea was that of spore germination. The spore balls were placed in 

 a number of different substances, including distilled water, tap water, 

 various sugar solutions, and potato infusions. The conclusion was soon 

 reached that the spores germinate quite readily in media, but prepara- 

 tions favorable for demonstrating germination are not so easy to obtain. 

 The demonstration of germination is, in fact, very difficult. The walls 

 of the spores are so opaque that it is usually impossible to determine in 

 unstained material whether or not a given cell has germinated. The 

 amoebae are quite small and hyaline. In liquid media they soon crawl 

 away from the spore ball, and may easily be confused with protozoa. 



The demonstration was finally accomplished by germinating the spores 

 on agar media in Petri dishes. When a rather dry agar is used as the cul- 

 ture medium, the amoebae remain, for a time at least, clustered around 

 the mother spore ball. This gives an opportunity to observe the colonies 

 produced by individual spore balls. When such material is fixed in 

 Flemming's weaker solution, embedded in paraffin, sectioned and stained 

 with the triple stain, it furnishes excellent opportunity for the study of 

 germination. In this way permanent slides have been made which 

 clearly show various stages of germination. Portions of germinating 

 spore balls are shown in Plate XXXIX, figures i and 2. Figure i shows 

 a small portion of a germinating spore ball from which some of the 

 amoebae are being set free. In one of the amoebae shown in this illustration 

 the nucleus can be clearly seen. The ungerminated spores are uninu- 

 cleate. Figure 2 shows a small colony of amoebae that have been set free 

 through a partial disintegration of the old spore ball. The small deeply 

 stained bodies are probably nucleoli; the nuclei can not be distinguished 

 in these amoebae. 



In some cases the spore walls of the entire spore ball disintegrate, set- 

 ting free as many amoebae as there were cells in the spore ball. Gener- 

 ally, however, the amoebae escape through openings in the walls of the 

 individual spores, and the spore ball is left almost intact. Numerous 

 spore balls showing nothing but empty walls can be seen in certain prepa- 

 rations. So far as has been observed, each spore contains only one nu- 

 cleus and produces on germination a single, uninucleate amoeba. The 

 amoebae are quite small, but under favorable conditions they grow rapidly 

 and divide. They move about by means of pseudopodia. Cilia have 

 not been observed. 



A very good method for obtaining abundant germination is as follows: 

 Mature spore balls taken from ordinary sori are dusted over the surface 

 of a nutrient agar, such as Lima bean or potato agar in Petri dishes, just 



