214 AGRICULTURAL EXPERIMENT STATION. [Jan. 



become closely intertwined, branching and increasing in 

 size until a compact structure is formed. This is at first 

 white, but its outer layers soon become changed, and their 

 cell walls thickened and blackened to form a protective rind 

 about the inner unchanged parts. A section through the 

 inner portion of a mature sclerotium shows that the con- 

 stituent threads have become so closely compacted that they 

 form a firm pseudoparenchyma (fig. 6). As they lie in all 

 directions, any section is sure to follow the course of some 

 of the threads, while others are cut at all angles. Thus the 

 apparent cells of the pseudoparenchyma vary in outline from 

 circular to much elongated. The cell cavities have abundant 

 protoplasmic contents, but neither starch nor oil can be rec- 

 ognized in them. When sections are sulniiitted to Errera's 

 iodine test, however, they prove to be very rich in glycogen, 

 which doubtless serves as a reserve food material for the 

 future development of the sclerotia. These bodies are to 

 be regarded, then, as resting mycelia, which serve the same 

 purpose as the resting spores of some fungi in tiding over 

 periods unfavorable to active development, and thus keeping 

 alive the species from season to season. 



In order to learn the history of their further development, 

 a numl)er of sclerotia were placed in moist chambers jNIay 

 26, a part on rather poor soil and a part on pure quartz sand. 

 Both lots were kept about equally damp, and stood side by 

 side in a north window ; but those on the sand began their 

 " germination" more promptly and carried it through more 

 satisfactorily. As those on the soil gave no results different 

 from the others, and were subsequently transferred to sand, 

 where they did much better, they will be neglected in the 

 following account. But it should l)e said that this result 

 was to be expected under the very artificial conditions of the 

 culture chamber, and cannot be held to be ecpially apjilicable 

 to the greenhouse. In a month one of the sclerotia on 

 quartz sand showed signs of further development. Two 

 slender stalks were growing upward from its upper side, and 

 two others were just breaking through its lower surface. 

 This would indicate that the points of origin of these stalks 

 are not determined by the amount of light to which they are 



