398 



THE AGRICULTURAL NEWS. 



Decemcek 10, 1910. 



FUNGUS NOTES. 



MISCELLANEOUS FUNGI 

 EXAMINED. 



RECENTLY 



Specimens of three interesting fungi have been received 

 recently at the Head Otiice from Mrs. Patterson in St. Vin- 

 cent. They con.sisted of smut of Guinea corn (Ustilaqo 

 sorghi (Link.) Pass), leaf spot of beet due to Cerco^^ora 

 betiriAa, Sacc, and rust of grape leaves {Uredo vitis, Thumen), 



USTILAGO soRGHi. This fungus attacks 

 the flowers of several species of the genus 

 Sorghum, and of cultivated sorghums such 

 as Guinea corn {A iidropoijon Sorghum, var. 

 imlgare). It occurs in Europe and America 

 as well as in the West Indies. The parts 

 affected are the ovary and stamens. The 

 former becomes swollen and projects some- 

 what beyond the surrounding glumes or 

 floral leaves. It takes the form of 

 a round-ended cylinder, white at the base 

 and brown from the middle upwards. The 

 brown colour is due to the fact that the 

 upper part of the ovary has been trans- 

 formed into a sac containing a mass of the YlG. 37. Ustil.^go .sorohi. patch of grey dead tissue, bounded by a red 

 spherical brown spores of the fungus. Hyperti'ophied Ovule attacked by the brown border. In some instances, the spots 

 After these spores are ripe, the wall of Fungus. become numerous, and run into — - 



this sac ruptures, and the spores are shed 

 freely into the air. When this happens, it is 



ating and producing the fungus again. According to 

 Brefeld, the brown spares will only germinate in a nutri- 

 tive solution, when they give rise to a promycelium and 

 .small lateral conidia, in the usual way. The first form 

 of germiuation is, however, n:ore probably that occurring 

 under natural conditions, as, in such circumstances, the 

 spores would not be able to obtain artificial culture media 

 in which to germinate. 



CERCOtiPORA BETicoLA. Thi.s fungus attacks severa 

 different varieties of the beet in Europe and America. Tlie 

 specimens sent were the leaves of the red garden variety which 

 are usually afl'ected to some extent, though 

 not as a rule very seriously. In moist 

 seasons, considerable damage may be in- 

 flicted on the sugar beet, but usually the 

 extent of the injury does not necessitate the 

 adoption of preventive measures. Where 

 the damage became extensive, spraying 

 with Bordeaux mixture was found to be 

 effective. 



The disease first appears in the form 

 of small brown spots, which extend until 

 they reach a diameter of about -J-inch or 

 more. They then consist of a circular 



Fig. 38. U.stilaijo soeghi. 

 Columella from the interior of 

 a diseased ovule. 



found that 

 there is a tapering cylinder of plant ti.ssue which has grown 

 upwards along the axis of the ovary from its base. This 

 cylinder terminates in 

 a blunt point before it 

 reaches the top of the sac. 

 In rare instances, it may be 

 branched once or twice, and 

 is then of a somewhat 

 irregular shape. The stam- 

 ens, when attacked, are 

 rendered entirely unrecog- 

 nizable. 



All the florets of any 

 one head are usually found 

 to be infected; moreover, 

 since the ovary is transformed in the manner already 

 described, it naturally follows that diseased plants produce 

 no seed. The disease does not, howevtr, appear to be of 

 any great importance, as no very large number of plants is 

 usually infected at any one time. For this reason no remedial 

 measures appear to have been 

 tried. 



When the spores are placed 

 in a drop of water, they germinate 

 and give rise to a short tube 

 or promycelium, which is usually 

 simple, Vjut may occasionally be 

 branched. According to Prillieux, 

 this does not form sporidia, as 

 is usually the case in members 

 of this genus (see Agricultural 

 News, Vol. IX, ]). .59), but is 

 divided up Viy cross walls into 

 a few cells. Eventually, the cells 

 separate from one another, form- 

 ing short, cylindrical, spore-like 

 rods, which are capable of germiti- 





r" 



Fig. 39. Ustilago sorghi. 



Fig. 40. Cercospoea beticola 

 Conidiophores and Conidia. 



run into one 



another, thus covering a large proportion 



of the leaf surface. In bad cases, the leaves blacken and dry 



up; as they do so they tend to stand more upright, 



and frequently become curled or rolled, thus pre.senting 



a characteristic appearance. 



The conidiophores of the 



fungus break through the 



epidermis in tufts, generally 



on the under surface of the 



leaf. They are short, with 



cross walls, often somewhat 



knotted at the tip, and of 



a brownish colour. Each 



bears a single somewhat 



... needle-shaped conidium. The 



Spores germinating in water, ^^^j^j^ ^^^ j^^^^ ^^^^j^j 



cellular, cylindrical and hya- 

 line, frequently drawn out into a point at the end. They 

 germinate verj' freely, and in a damp year the spots on 

 the leaves increase rapidly. In (ierinaiiy, the fungus is said 

 to attack the leaf stalks, bracts and pods, as well as the 

 leaves, and it seems possible that infection may be carried 

 by means of spores on the seeds. 



UEEDOviTis. This fungus 

 forms yellow, powdery pustules 

 on the leaves of grape vines, 

 usually on the under side. It was 

 first reported from the United 

 States of America, where, however, 

 it did not cau.se any very serious 

 damage, and subsequently disap- 

 peared. In 1879 it appeared in 

 .Jamaica, where it assumed the 

 form of a serious disease, and 

 attracted considerable attention 

 during that and a few subsequent 

 years. 



The fungus was investigated 

 by Massee, who identified it. 



