316 THE RUSTS OF NOVA SCOTIA. FRASER. 



The mycelium often produces abnormal growths. The 

 most conspicuous in this region is the "witches' broom" of the 

 balsam fir and the elongated and abnormally thickened stems 

 of the bluberry due to the telial stage of Calyptospora colum- 

 naris. Some species of the genus Gymnosporangium produce 

 spherical galls on the cedar, but they do not seem to have been 

 collected in Nova Scotia. In these cases the mycelium is per- 

 ennial, but even localized mycelium may produce swellings 

 and deformation especially in the stalks and midribs of the 

 leaves. This is so in the case of the aecial stage of Puccinia 

 sambuci which is common in the spring on Sambucus 

 canadensis. 



Pycniospores. 



The pycniospores are produced in a pycnium (pycnidium, 

 spermagonium) which is a small inconspicuous, punctiform 

 body. It is usually flask-shaped averaging 100-150^ in 

 diameter, formed immediately beneath the epidermis, with the 

 narrow neck protruding in order to discharge the spores into 

 the air. Usually the opening is provided with a small tuft 

 of hairs. Sometimes the pycnium is formed immediately 

 beneath the cuticle and is then more or less hemispherical or 

 conical. The pycnia are usually on the opposite side of the 

 leaf from the spore-form accompanying them, but sometimes 

 on the same side when usually they surround the accompany- 

 ing form. Their position, arrangement, form, color and size 

 are characters of some taxonomic value. Usually pycnia 

 appear after infection by basidiospores without any regard to 

 the kind of spore that is to follow: thus, though they usually 

 precede the aecia, they may accompany the other spore forms 

 when aecia are wanting. 



The pycniospores are very small, oval or rounded bodies a 

 few microns in length (about 5-8ft). They are produced 

 within the pycnium in short chains from converging hyphae 

 and are held together by a viscid sugary secretion, which some- 

 times attracts insects. As far as is known these spores havfi 



