THE PAKASITKJ EXOASCEAE. 157 



Exoascus communis Sad. This produces pocket-plmiis on 

 I'm HUH (/ineriaoix, P. pamila, and P. maritima in America. 



Similar " pockets " also occur on Primus subcordata, P. Chicasa, 

 and P. jminsylvaiiim, in America, as a result of some Broascus. 



Exoascus Farlowii Sad. produces similar 

 deformation of carpels and floral envelopes on 

 Primus serotina in North America. 



Exoascus Johansonii Sad. produces carpel- 

 eidargement on the female catkins of Populus 

 tirmula, P. tremidoidcs and P. (jirmdidetitata; the 

 contents of the asci are yellow. (Fig. 52.) The 

 anatomy of the deformed ovaries has just been 

 described by Sadebeck.^ 



Exoascus rhizophorus Johan. causes similar fw. bi.-Exoaicus 



,.,,., 1 . f Ti 7 Johansonii Sad. on 



enlargement ot the icmale catkins oi Po/Jiilus Popuiv.stremv.ia. (v. 



,, ■* Tubeufdel.) 



(dl)ii. 



Exoascus alni-incanae Ktihn {Ex. amentorum Sad.) This 

 species is readily distinguished by the absence of a stalk-cell 

 on the ascus. It causes increased growth and enlargement 

 of the seed-scales of alder catkins, the fruit itself being seldom 

 attacked. The fleshy bladder-like outgrowths at first appear 

 as little red processes ; later, the asci are developed on the 

 outer surface as a whitish coating. On many of these red 

 processes may still be recognized the trifid apex of the normal 

 .scale, (this is really formed from five smaller scales fused into 

 a single large one with a trifid apex). A number of these 

 red outgrowths are generally present on each infected catkin, 

 yet the alders continue to flower vigorously every year. 



Wakker,- in investigating the anatomy of the deformed scales, 

 found the following alterations : — the scales are increased to many 

 times their original size and contain two cavities; all parenchy- 

 matous cells become regular and iso-diametric ; lignification of 

 the elements of the wood is more or less interfered with, and 

 fewer wood-fibres are produced ; there is an accumulation of 

 transitory starch. 



Exoascus alni-glutinosae Tubeuf. This is a new species 

 distinguished by v. Tubeuf iu 1895. It occurs in the Sudetic 

 mountains, Italy, Denmark, and Sweden, on Alnus rjlutinosa. 

 Its habit is similar to that of Ex. alni-incanae, but the asci 



^ Sadebeck (See Literature), 4. p. 144. - Prinrjiheim'-i Jahrhnch, 1892. 



