552 



HUTCHINSON'S POPULAR BOTANY 



Hawthorn, Pear, and Whitebeam may often be found swollen and scurfy. 

 The leaves and fruit are subject to the same diseased condition. Examina- 

 tion with a lens will show that this spindle-shaped orange swelling consists 

 of a crowd of cluster-cups. Formerly it was considered as a distinct species 

 under the name of Rcestdia lacerata. Under the bark of Juniper in autumn 

 there develop teleutospores of Gymnosporangium clavariceforme, and in the 



following April or May 

 these burst through 

 the bark as cylindri- 

 cal or tongue-shaped 

 masses of pale orange 

 jelly. This stage is 

 perennial on the Juni- 

 per, and the spores are 

 carried by the wind to 

 the Hawthorn, etc., 

 where they develop 

 and give rise in the 

 autumn to the cluster- 

 cups of Rcestelia lace- 

 rata, which is not per- 

 ennial but only tem- 

 porary. 



One other example 

 of this heteroecism may 

 be mentioned. The 

 Silver Fir suffers from 

 a fungoid disease 

 known as Pine-shoot- 

 twist (Geoma pinitor- 

 quum\ and the Larch 

 from Larch-leaf-rust 

 (Ceoma laricis). On the 

 leaves of Aspen may 

 be found minute 

 b r o w n i s h-y e 1 1 o w 

 cushions known as 



Melampsora, tremula, Now these three plant diseases are all caused by one 

 Fungus, whose teleutospores are produced on the Aspen-leaves and carried 

 by the wind to both Silver Fir and Larch, where they produce other stages 

 in the cycle. 



The Ustilaginese are similar to Uredinese in the fact that they are para- 

 sites entirely on herbaceous plants. The mycele is deep-seated in the tissues 

 of their victims, running along the intercellular spaces and often thrusting 



FIG. 698.- STONEWOBT (Chara fragilis). 



(a) Portion of the plant in fruit; (6) fertile leaf with spherical antheridia and 



spirally walled archegonia ; (c) antheridium ; (d) archegonium ; (e) spore; 



(/) antherozoid. 



