1889.] MICROSCOPICAL JOURNAL. 179 



found in the centre of the bed. The aacidiospores are abstricted in the 

 manner common to conidia, thebasidia being septate almost as soon as 

 microscopically visible. 



In many ascidia, yEcidium berberidis especially, it is quite common 

 to find apparently ordinary filaments (fig. 3, c) protruding from the 

 stomata, which are situated above the ascidium fruit, as it forms beneath 

 the epidermis. Many spermatia may often be seen adhering closely to 

 these bodies. If a sexual process is still to be sought these occurrences 

 deserve close attention. There may, perhaps, be a general hyphal 

 fecundation through these organs. I am inclined, however, to consider 

 the extension of the hyphse through the stomatal openings as merely 

 accidental. 



H. Marshall Ward, in his paper " On the sexuality of the fungi," 

 makes the statement that "it is probable that the sexuality of the higher 

 fungi has disappeared, because its purpose has been equally well or 

 better attained otherwise than by means of sexual organs ; " that is, for 

 some reason they have become apogamous,* an asexual spore formation 

 has displaced a sexual process "while the fruit still retains in general a 

 sexual form. This I think to be true of the uredines ; though the fruit 

 may be morphologically analogous to the sexually-produced fruit of 

 other Ascomycetes, the spores are asexually produced. 



So far as is known, the sexual process is chiefly one for re-invigora- 

 tion, that the life of the species may be continued unimpaired. While 

 in the great majority of plants this is accomplished by the formation of 

 a new plant body by the union of two more or less specialized masses 

 of protoplasm, constituting the sexual process, it seems that some, be- 

 cause of certain favored conditions, are able to do away with this special 

 method, being able to draw sufficient nourishment from their more ex- 

 cellent food supply. In the parasite the source of energy is the nour- 

 ishment obtained from the host, and the better the connection between 

 the parasite and its host the less liable is the protoplasm of the former 

 to suffer vitiation for want of nutrient matter. 



In the Uredineas the union of the host and parasite is almost perfect,! 

 and in those species in which the whole development is upon one host 

 it is probable that the wants of the fungus are adequately met. That 

 some species are heteroecious upon particular but diverse host species 

 is, we think, but indicative of the fact that the combination best com- 

 plies with the nutritive needs of the parasite not to be fulfilled by one 

 host alone. 



Bibliography. — The full bibliography of the subject is much too ex- 

 tensive to be listed here, but the following books and papers are men- 

 tioned as having been specially valuable in the preparation of this article : 



Burrill, Parasitic Fungi of Illinois. Bull. III. St. Lab., ii, 1S85, 

 pp. 141-255. 



De Bar-y, Morphology and Biology of the Fungi, Mycetozoa and 

 Bacteria, 18S7. 



Dietel, Morphologie und Biologie der Uredineen. 



Farlow, Gymnosporangia or Cedar Apples of the United States, 1S80. 



Massee, On the Presence of Sexual Organs in ./Ecidium. Annals 

 of Botany, ii, 1888, pp. 47-51. 



*Vines, Plant Physiology, p. 636; De Bary, Morphology and Biology of the Fungi, p. 123. 

 t Sub-epidermal Rusts, I. c. 



