CUCUMBERS, TOMATOS, AND FUNGUS PAEASITES. 



148 



be caused by Dendryphium comosum, Wallr. Further investigation 

 showed the fragments of manure projecting from the soil in which 

 the plants were growing to be covered with a copious development of 

 Dendryphium, and the fungus was finally traced to the manure-heap. 



Previous to the present record Dendryphium has never been known 

 to act as a destructive parasite ; and its becoming so in the present 

 instance is entirely due to its accidental introduction, along with the 

 manure, to a set of conditions which enabled it to assume a parasitic 

 existence on plants predisp3sed to disease. Experiments conducted at 

 Kew prove conclusively that Dendryphium cannot attack Cucumber plants 

 growing in a cool frame. It may be added that the Dendryphium has 

 not only spread throughout the house where it originated, but has also 

 attacked Cucumbers in two other nurseries owned by the same gardener, 

 the spores having been carried by clothing, tools, &c. from one place to 

 another. 



No records of the occurrence of this newly created parasite are as 

 yet to hand from other localities than those enumerated, but now that 

 its parasitism is established it is likely to extend its area of devastation. 



The use of fungicides in the form of sprays has not by any means 

 produced the results desired and anticipated, and extended experiments 

 have demonstrated that, under the conditions necessary for the rapid pro- 

 duction of Cucumbers, the daily syringing and constantly damp surface of 

 the foliage render useless those fungicides which, when applied under 

 more favourable conditions, have proved effective. 



Under the circumstances a series of experiments have been carried 

 out with the object of ascertaining whether some substance taken up by 

 the roots of Cucumbers and Tomatos would not render plants thus treated 

 immune against the attacks of fungus parasites, without at the same 

 time exercising any injurious or retarding effect on growth or on the pro- 

 duction of fruit. 



From among the various substances tested, sulphate of copper 

 (CuS0 4 ) alone met all the above-mentioned requirements. 



The following is an outline of the mode of treatment of plants ren- 

 dered immune by the use of sulphate of copper. 



The Cucumber and Tomato seed was sown, and the plants grown 

 throughout in a stove, having a mean temperature of 75° F., the 

 humidity varying between 79° and saturation point. The potting, water- 

 ing, spraying, and general treatment were left entirely to a gardener, and 

 consequently was conducted along the lines followed in establishments 

 where the fruit is grown for sale. 



The Cucumbers were of the varieties known as ' Telegraph ' and 

 ■ Every Day,' and the Tomatos ' Up to Date ' and 'Main Crop.' Three 

 hundred Cucumber seedlings and an equal number of Tomato seedlings 

 were subjected to experiment, fifty of each kind being used as check 

 plants. When the seedlings were a fortnight old, the Cucumbers were 

 grouped round eight large Cucumber plants badly attacked by Ccrcospora 

 melonis, Cke., and Dendryphium comosum, Wallr.. and the Tomato seed- 

 lings were arranged around a Tomato plant bearing numerous blotches 

 on the leaves caused by Cladosporium fulvum, Cke. At this period the 

 specific course of treatment commenced, which consisted in watering the 



