284 BOTANY. 



Podospheera Kunzei may be fouud on tlie leaves of the cherry and 

 apple, which it injures greatly in some cases ; the couidia may be ob 

 served in midsummer, and the sexual process and formation of perithecia 

 in autumn. 



Phyllactinia guttata may be obtained in great abundance in autumn 

 upon the leaves of the hazel and ironwood. 



Uncinula adunca is frequently abundant on willow leaves in the 

 autumn (Fig. 190). 



U. spirulis is the species to whose conidial stage the name Oidiii)i> 

 Tuckeri has hitherto been applied in this country. It occurs on the 

 grape, and does great injury. According to Dr. Farlow, it is not cer- 

 tain that the so-called Oidium Tuckeri of this country is identical with 

 what is so named in Europe, and which is even more injurious to 

 grapes in that country than in this. 



U. circinata occurs on the leaves of the red and silver maples in the 

 autumn. 



MierospJiara Friesii is one of the most common species. It may be 

 found in the conidial stage at any time during the summer on the 

 leaves of the lilac, and late in summer or in autumn the perithecia are 

 usually abundant. 



M. txtensa is a nearly related species, often very common on oak 

 leaves. 



Erysiphe lamprocarpa, \vhich may be found on Composite (especially 

 on Helianthus), and also on wild verbenas, is readily distinguished by 

 its two-spored asci. The commonness of this species makes it a valua- 

 ble one for study. 



E. tortUis may be frequently obtained on the leaves of the Virgin's 

 Bower. 



E. Ma/rtii occurs in great abundance upon cultivated peas, greatly 

 to their injury. In summer it covers the leaves and fruits with a 

 white mould-like growth, which is the conidial stage of the parasite ; 

 as autumn approaches the mycelium becomes darker, and finally large 

 numbers of perithecia may be found. 



E. communis appears in early summer on grass leaves, where the 

 vegetation is rank. In autumn the perithecia may be found in abun- 

 dance on Uammculaceae (especially on Anemone) growing in grass. 



SAPROPHYTIC PLANTS. 



Eurotiwn Tierbariorum may be readily obtained for study by placing 

 a few green specimens of Phanerogams in an ordinary plant-press and 

 permitting them to remain until they become mouldy. The conidial 

 stage, which first appears, is what has long been described as a distinct 

 fungus under the name of A&pergittm glancii* ; somewhat later the 

 bright yellow perithecia will be found in abundance, 



