138 



THE CANADIAN HORTICULTURIST. 



as sausage-shaped swellings 

 filled with spores. (Fig-. 1777). 

 Remedy. — - The only avail- 

 able remedy is the destruction 

 of the tree, so that the disease 

 may not spread to other trees. 



(e) Cedar Apple and Apple 

 Rust {Gymnosporangiuin and 

 Roestelia). (Fig. 1778). It is 

 well known that certain stages 

 in the life of the rust of wheat 

 (Puccinea graminis) are passed 

 on the wheat and the other 

 stage on the barberry. The 

 parasite which causes "apple 

 rust " passes part of its life on 

 apple leaves as Roestelia, and 

 the other stage on the cedar 

 or juniper as Gynmosporan- 

 giiim. Nme species are known 

 in this genus : two on white 

 cedar only, three on red cedar 

 only, two on both white and 

 red cedars, one on the com- 

 mon juniper, and one on the 

 western juniper {J. occiden- 

 falis). The mycelium is per- 

 ennial in most species, and the 

 abnormal growths depend to a 

 certain extent on the part af- 

 fected and the rate of growth 

 of the fungal threads. Growths 

 on the affected leaves are called 

 " cedar apples." (Fig. 1778). 

 Distorted branches are very 

 common forms of the disease, 

 and are known as " witches" 

 broom." The resting spores 

 produced on the cedars and 

 junipers, under favorable conditions, germin- 

 ate and soon liberate spores of a slightly 

 different nature. These, falling on the leaves 

 of the apple, produce the " apple rust." 



(f) Lichens. — Lichens are extremely com- 

 mon on all kinds of trees. They form incrus- 

 tations on the bark, and may be either 



Fig 1777- Peridermium pini (Pine Cone Fungus), (a) leaves of 



pine affected with this disease. The cluster cups occur as 



orange yellow blisters and contain the spores. Spermo- 



gonia (b) appear as black spots. (B) shows a branch 



which has been killed and which bears cluster 



cups. (After Massee). 



leathery or semi-gelatinous in texture. It is 

 conceded by most authorities that the lichens 

 do not get their nourishment from the trees 

 they incrust, but use their position on the 

 bark as a means of getting a better livelihood 

 from the air. The surface of the lichen is 

 specially adapted for absorbing dew, rain or 



