144 FAMILIAR TREES 



by hand, and the -maturity of the seed be tested by 

 opening one or two of the capsules, and observing 

 if the cotyledons are green and succulent. It is 

 advisable to keep the seeds unsown tintil spring, since 

 moles eat many of those sown in autumn ; but those 

 of our common species seldom germinate until the 

 second or third year. They should not be covered 

 with more than half an inch of soil 



Besides being occasionally blotched in autumn by 

 the attacks of the black fungus Rhytis'rna aceri'num, 

 so universal on the Sycamore, the leaves of the Maple 

 are also commonly disfigured either by a mildew or 

 by a gall. The Maple blight or mildew (Unci'nula 

 bicorn'is) gives the whole plant a hoary appearance, 

 as if sprinkled with powdered chalk, both surfaces of 

 the leaves being alike affected ; but this disease must 

 not be confounded with an unhealthy condition 

 formerly attributed to another fungus, and known 

 as Eri'neum aceri'num, which in spring produces 

 patches of pinkish or violet hoariness on the under 

 surfaces of the leaves, glistening like hoar-frost. 

 With equal frequency the leaves of the Maple are 

 seen to .be thickly studded on their upper surfaces 

 with red conical swellings. These are the results of 

 the punctures of a mite (Phytop'tus myria'deum), 

 and they are interesting as an example of the 

 general rule that when such irritation occurs, as 

 is also seen in the galls on the Rose and the 

 Violet, if a pigment is produced it is one which 

 the plant is prone to develop normally either in 

 flower or leaf. 



