TAPHRINALES 165 



hagen, 1895). The first line, with clavate asci on ferns, has not been 

 carefully studied. The second line with blunt, cylindrical asci more or 

 less flattened at the top, on Amentiferae, includes T. Tosquineti on the 

 leaves and female catkins of Alnus, T. aurea which causes saccate pro- 

 trusions on leaves of Populus and forms yellow hymenia on their concave 

 lower surfaces, and T. Carpini which stimulates the twigs of Carpinus 

 betulus to the formation of witches' brooms. A third line with clavate 

 to narrow cylindrical asci more or less rounded at the top, on Rosaceae, 

 includes numerous species important in phytopathology, as T. Pruni, 

 T. institiae and T. Cerasi on Prunus. The hyphae of T. Pruni live in the 

 branches of plums and at flowering grow into the young fruits which 

 undergo an abnormal development, Instead of forming a stone and 

 outer fleshy layer, the fruit wall assumes a waxy, coriaceous character, 

 and the whole fruit is a deformed, unpalatable structure. In these, the 

 hyphae come out between the epidermal cells and branch between 

 epidermis and cuticle to such a degree that the whole fruit is covered by 

 ramose short-celled hyphae which subsequently become chlamydospores. 

 T. institiae on plum and T. Cerasi on cherry stimulate the host to the 

 formation of witches' brooms; T. deformans causes leaf curl of the peach. 



The Taphrinales show relationships to the Protomycetaceae. As in the 

 latter, intercalary chlamydospores are formed on the mycelium, singly 

 in the Protomycetaceae, serially in the Taphrinaceae. As in the Proto- 

 mycetaceae, these chlamydospores germinate with an ascus; only in 

 most Protomycetaceae the endospore separates from the exospore, 

 while their connection continues in the Taphrinales. The separation 

 of the ascus from the stipe cell, regarded in this light, might be considered 

 as a subsequent device to prevent the retreat of the protoplasm. In 

 both families the ascospores arise in a protoplasmic peripheral layer; in 

 Taphrina the chlamydospore generally shows a simple zygote, in Pro- 

 tomyces (if this interpretation is permissible) a coenozygote, and, as in the 

 Protomycetaceae, the ascospores germinate to a sprout mycelium. 



Which of these families may be considered as primitive and which 

 derived, and whence their derivation, is still obscure. The simplest 

 form so far investigated is T. (Magnusiella) Potentillae which lacks 

 true chlamydospores; whether it is next the ancestral form, may not be 

 determined at present. In any case, the Taphrinaceae form a very 

 old family, as may be concluded from their biological relationships, 

 especially from their adaptation to hosts. 



