452 



SCIENCE 



[N. S. Vol. XXX. No. 770 



Bulletin will be limited to technical treat- 

 ments of subjects of advanced research. This 

 will make most of the articles of that publica- 

 tion also beyond the comprehension of the 

 average pupil of the above grades of schools, 

 and make the bulletin only appropriate for 

 the libraries of colleges and universities. 



tomentosa and Pirus communis silv., but 

 placed the fungus in the genus Stigmatea, one 

 of the Sphseriales closely related to the Sphce- 

 rella but differing chiefly in the possession of 



SPECIAL ARTICLES 



THE PERFECT STAGE OF LEAF-SPOT OF PEAR AND 



QUINCE 



It is well knovm that the " leaf -spot " of 

 the pear and quince is caused by an " imper- 

 fect fungus" called Entomosporium macu- 

 latum Lev. The perfect stage, however, is 

 not so well known, although it is probably 

 very common in both Europe and this coun- 

 try, but may be easily overlooked. It occurs 

 quite abundantly on the leaves of the pear 

 and quince, affected with the disease, which 

 have lain on the ground during the winter. 

 Such leaves are very commonly affected in the 

 spring with species of Sphcerella, as S. sentina 

 and S. pyri. These two species are also " per- 

 fect " stages of fungi, but very different from 

 the perfect stage of the leaf-spot caused by 

 Entomosporium. Their fruit bodies are 

 black and project slightly from the surface 

 of the dead leaves and thus are quite con- 

 spicuous objects even on the dry leaves when 

 examined with the pocket lens. 



The fruit bodies of the perfect stage of 

 Entomosporium are, however, usually very in- 

 conspicuous and are not easily, if at all, rec- 

 ognized with the aid of a pocket lens, in the 

 dry state, because they are collapsed. When 

 the leaves are wet, however, and the fruit 

 bodies are mature, their contents are swollen 

 and thus crowd apart the thin wall and ex- 

 pose the white tips of the asci in a more or 

 less elliptical area. This character of the 

 fruit body shows that the fungus is one of the 

 Discomycetes. The asci are eight-spored, the 

 spores hyaline and two-celled, while the asci 

 are accompanied by paraphyses. Sorauer' 

 first called attention to the perfect stage of 

 Entomosporium on leaves of Cotoneaster 



' " Pflanzenkrankheiten," Zweite Auflage, 2, 372- 

 .377, 1886. 



Twelve years ago I called attention to this 

 perfect stage which I found on quince leaves 

 at Ithaca, and identified as Fahrwa,' at the 

 same time pointing out how easy, under cer- 

 tain conditions, it might be to mistake it for 

 a Stigmatea. The connection of the fungus 

 with the Entomosporium by Sorauer was as- 

 sumed because it follows the Entomosporium 

 during late autumn and in the spring in the 

 same tissues of the leaf. While I have several 

 times grown the Entomosporium from quince 

 fruit in pure cultures, I have never obtained 

 the perfect stage in these cultures. I have, 

 however, carried the cultures in the opposite 

 direction, by obtaining the Entomosporium 

 in pure cultures from ascospores of the 

 Faircea. 



I hope before long to publish a full account 

 of these studies, but in the meantime it seems 

 desirable to indicate the name of the fungus 

 in its new position. Sorauer's studies were 

 concerned with Entomosporium mespili (DC.) 

 Sacc, and he employed the name Stigmatea 

 mespiW (DC.) Sor. This fungus would 

 therefore be Fabrosa mespili (Sor.) while the 

 one I have worked with {Entomosporium 

 maculatum (Lev.)) becomes Fahrwa maculata 

 (Lev.). There is a strong probability that 

 these two species are identical, since the only 

 difference between Entomosporitim maculatum 

 Lev., and E. mespili (DO.) Sacc, aside from 

 differences in size of the spores and these 

 will not, it appears, hold, as given in the de- 

 scriptions, is that the lateral cells of the spore 

 are depressed in the former, while they are 

 a little larger and more rotund in the latter. 

 Geo. F. Atkinson 



Depaetment op Botany, 

 Cornell Univebsity 



- " Leaf-spot of Pear," Garden and Forest, 10, 

 73-74, 1897. 



" L. c, p. 371. See also Sorauer, P., " Handbuch 

 du Pflanzenkrankheiten," Dritte Auflage, 2, 237, 

 1908, where the perfect stage is given as Stigmea 

 mespili Sor. 



