262 THE BOTANICAL MAGAZINE. [Vol. xxix. No. 346. 



was made on the young leaves of Picea Glehni and excelsa in 

 the Botanic Garden. The experiments all ended in negative 

 results, aud so the matter was left till 1912. 



In 1912, Mr. Masamori Arita kindly sent us an excellent 

 specimen of a Peridermium on Picea ajanensis which was collect- 

 ed also at a National Forest near Ochiai. He informed us, that 

 the air of the forest, when he went there at about the middle 

 of July, was literally full of the dust\ r orange-colored spores 

 in a windy day. 



On hearing this report, the author started at once and 

 reached the forest on the 28th of July. The forest is famous 

 for the stately trees of Picea ajanensis and Glehni, and also of 

 Abies sachalinensis (3, 11, 12). As their undergrowth, Rhodo- 

 dendron hrachycarpum is growing luxuriantly. When we reached 

 there, the aecidiospores had almost all been dispersed, leaving 

 white peridial walls behind. One thing which struck the author 

 as most remarkable is the fact, that Picea Glehni is perfectly 

 immune to the species of Peridermium which affects Picea aja- 

 nensis. Of small trees of these two species of Picea growing 

 side by side among the Rhododendron bushes, the Ajan spruce 

 alone was badly affected, while the Glehn's spruce remained 

 perfectly sound. 



A comparatively study of the peridial cells and aecidiospores 

 of these two forms of Peridermium on Picea ajanensis and Glehni 

 revealed the fact, that they are of two different species. They 

 differ from each other in the size and shape of the aecidiospores 

 as well as in the marking on the wall of the peridial cells. 



It was found afterward that Peridermium on Picea Glehni 

 is always associated with Chrysomyxa on Rhododendron dahu- 

 ricum, and that it most likely corresponds to the European C. 

 Rhododendri. 



The only species of Peridermium already known to grow 

 on the Japanese spruces is P. Picea^-hondoensis Diet. (6), which 

 was collected for the first time by Prof. Kusano on the leaves 

 of Picea hondoensis Mayr (11) on Mt. Fuji in Aug. 1903. Ac- 

 cording to Masters and Beissxer (3), Picea hondoensis Mayr 

 should be considered as a variety of P. ajanensis. It is . now 



