The Life History of Pohi:hrincium Trifolii Kiinze. 221 



July, 192 1, but onh- 10 per cent, of the conidia germinated. 

 The germ tube is at first colourless. Many instances were seen 

 of conidia germinating on leaves taken from infected plants and 

 twice germ tubes were seen penetrating stomata. Further, the 

 host was also seen to be entered by a germ tube penetrating the 

 cuticle of an epidermal cell. Here penetration occurred as in 

 the penetration of Vicia Faba by Botrytis cinerea as recorded 

 by Blackman and Welsford, i.e. \Wthout the formation of anv 

 appressorium(3): these authors suggest the cuticle is ruptured 

 mechanically by the pressure of the tip of the germ tube. 

 Attempts were made to infect clover plants gro\Mi in pots in a 

 greenhouse and also plants in their natural surroundings, but 

 none was successful. The failure of these experiments suggests 

 that conidia do not readily infect plants except perhaps under 

 speciaUsed atmospheric conditions, and no doubt the physio- 

 logical condition of the leaf plays an important part. It has 

 been noticed that infection does not spread rapidly amongst 

 clover plants in the field; since, under all weather conditions, 

 although plenty of infected leaves could be found in the infected 

 area, the disease was not present in anything approaching an 

 epidemic form during the two and a half years that the plot was 

 observed carefully. 



In Julv, 1921, a clover leaf just showing traces of infection 

 was placed in a room with its petiole in a glass of water and kept 

 under observation for seven days. When first examined the 

 leaflet was found to have five small specks, denoting conidial 

 stromata; apart from this it was quite healthy. A week later 

 the whole leaflet had become very pale, except for the midrib 

 which remained green, and the leaflet was found to be covered 

 with black conidial stromata, bearing conidiophores and obovate 

 conidia. Three of the five original compound stromata {a, b 

 and c) were especiallv watched, their increase in growth recorded 

 after five days being as follows : 



Compound Xo. of 



stroma Date infection spots Remarks 



a July 7th 17 — 



,, nth 30 Area nearly doubled in five days 



b ,, 7th 3 Stroma tumid and colourless, one 



infection spot mature and black, 

 the rest colourless 

 „ nth 17 Original infection had sent out 



14 h\-phae to produce 14 fresh 

 infection spots, and had increased 

 in area nearly six times 

 c „ 7th 7 Stroma colourless, infection spots 



black 

 „ nth 36 Stroma entirely black, from one 



infection spot a tendril of pycno- 

 spores was exuding 



