484 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



in his exsiccatse labelled Helminthosporium gracile and referring the 

 species to Wallroth.* It would be most illogical to accept de 

 Thumen's name, as there is no description, and, further, the plant dis- 

 tributed is clearly different from Wallroth's diagnosis. It is obvious 

 that the name Heterosporium echinulatum cannot be used for the species, 

 as it has been previously used for another fungus, as shown above. 



Saccardo himself reahzed his misdetermination, and in his 

 " Sylloge " (iv. p. 480) refers the species to that of Wallroth as de 

 Thumen had previously done. The descriptions clearly show, as 

 pointed out above, that Wallroth's plant is entirely different and is 

 the modern Brachysporium gracile. The specific name gracile, therefore, 

 as appUed to Heterosporium, having really no connexion with Wall- 

 roth's description, can be used for the fungus diagnosed by Saccardo. 



Thus the synonymy for the species is Heterosporium gracile Sacc. 

 Syll. iv. (1886), p. 480 = Heterosporium echinulatum Sacc. Mich. ii. 

 p. 364, non (B. et Br.) Cooke et auct. 



Description of Spores. — The mature spores vary in length and 

 breadth. They measure from 30-80 fju in length and 15-20 fx in 

 diameter, are oblong-cyUndrical, with rounded ends, and are sHghtly 

 constricted at the septa. The average spore has two septa, but con- 

 tinuous, uniseptate, triseptate, and even occasionally quadriseptate 

 spores occur (fig. 106). The epispore is studded with small projecting 

 warts. The conidia are at first colourless, but gradually assume a 

 pale olive colour, and finally become brownish-olive. The warts are 

 developed while the conidia are in a young state, and septa appear 

 to be formed after the conidia have reached their full size (fig. 106, b). 



Germination of Spores. — The germination of the spores was observed 

 in spores taken from Iris leaves and placed in watch-glasses, and also 

 in hanging drop cultures in various media, the spores in the latter 

 case being obtained from pure cultures. The spores were taken from 

 the cultures by means of a platinum needle, previously sterilized by 

 heating, and dispersed in a drop of sterile water upon a sterilized glass 

 slip. By repeating the operation a few times enough spores were 

 present to ensure one to four being transferred by one dip of the 

 needle to the hanging drop. The media used were steriHzed water, 

 2\ per cent, cane-sugar solution, prune juice, glucose agar, and prune- 

 juice agar. The germination was similar in all the media. Spores 

 sown at 9.30 A.M. pushed oat germ tubes by 2 p.m. of the same day. 

 Sometimes the germ tube arose from the end cell and at other times 

 from the middle. The next afternoon, i.e. after about thirty hours, 

 practically every cell had produced a germ tube, and it will be seen 

 from the illustrations that a two-celled spore was capable of pro- 

 ducing three, and a three-celled spore as many as five germ tubes 

 (fig. 106, c-f). The hyphae had grown greatly in length and had a 

 characteristic waviness. It was also noticed that in several instances 

 the hyphae had become branched and septate after attaining a length 

 of 200 fjb on solid media and 250-300 fi in hquid media. 



* Mycoth. Univ., Nos. 666 and 876 : Fung. Austr., No. 1066. 



