THE RUSTS OF NOVA SCOTIA. FRASER. 317 



no function nor any connection with the further development 

 of the fungus. They may be made to grow and bud in a 

 nutrient solution but nothing further has been obtained. It 

 may be that they had some sexual function that has been lost, 

 but there is not much evidence to support this view. 



The pycnium is rarely absent in the life cycle, but it only 

 occurs once, not being repeated with each generation. If the 

 aecia repeat, spermagonia only occur with the first generation. 

 If the pycnium accompanies the uredinia it does not repeat. 

 In the case of the teliospore it has not been established whether 

 it accompanies each generation or not. 



Aeciospores. 



The mycelium, which results from the entrance of the 

 germ tube of a basidiospore after it has produced a certain 

 number of pyciiia, soon develops aeciospores. Within the 

 plant tissues hyphae collect together into a compact mass grow- 

 ing perpendicular to the surface of the host, and from the 

 closely crowded hyphae the spores are cut oft' in basipetal 

 succession so that they are produced in chains. At first- 

 sterile cells alternate with the spore cells, but these usually 

 disappear by the time the spores are mature. The outer layer 

 of hyphae usually becomes a wall or peridium, which surrounds 

 the spore mass, and after the rupture of the epidermis usually 

 becomes cylindrical or cupshaped. Sometimes the peridium is 

 absent or it may be replaced by paraphyses as in the genus 

 Phragmidium. The spore mass with its peridium or para- 

 physes is called an aecium or aecidinm. The spores are at 

 first polyhedral from mutual pressure, but they soon become 

 free and are then usually globose or ellipsoid in shape. The 

 wall is usually colorless (deep brown in the genus 

 Gymnosporangium,') with verrucose sculpturing. The rough- 

 ened wall aids the spores in adhering to the host plant. The 

 contents are chiefly orange-red or orange-yellow and in many 

 cases soon become colourless. Eventually the aecia rupture the 



I'KOC. & TRANS. N. S. INST. Scr., VOL. XIT. THANK. 22. 



