The Scottish Naturalist. 21 1 



saucer in \^ater. I have found seeds thus sown, and with the 

 water mixed with the pulverised turnip clubs of the previous 

 year, to have their roots attacked when only about the thickness 

 of one-hundredth of an inch. But in such circumstances the 

 tap-root itself, even where no cause of disease has been intro- 

 duced, never attains to any kind of bulb, or to a thickness be- 

 yond two or three hundredths of an inch ; so that when attacked 

 by the fungus in water, the portion of the root affected, not 

 growing so rapidly as to afford room for the disrupting plasmodia 

 of the fungus, is speedily killed, and goes into disintegration. 

 But the club ceases to enlarge whenever the root dies. Could 

 the granular plasma of the fungus grow upon decaying matter, 

 there seems no reason why the club should not go on enlarging 

 after the death of the root. But if it is a parasite the reason is 

 plain ; it cannot live on dead matter. 



It is, however, when the seeds of the turnip are planted in 

 earth that some of the phenomena can be best observed. I find 

 that the ripe spores of the fungus exist as spores from one season 

 to another. During the intense frosts of last winter (1878-79) 

 they remained as bright and clear as when newly matured. 

 They are not to- be killed by being turned up to the frost. I 

 mixed a quantity of the rotten clubs of crop 1878 containing 

 these spores w^ith garden mould in which no disease existed, and 

 with the mixture filled a number of pots, some having drainage 

 and some having close bottoms. Good turnip seeds, not known 

 to be in any way defective, were sown in the pots. All the re- 

 sulting plants became at an early stage excessively and fatally 

 clubbed. The two largest pots, having the ordinary flower-pot 

 drainage, and standing in the open air, had each between thirty 

 and forty plants all clubbed, while the turnips in the same garden 

 mould beside them were quite free of disease. The plants in the 

 pots which had no drainage, and which from the wetness of the 

 season were frequently soaking in water, had a large develop- 

 ment of lateral roots : they did not grow so rapidly as the plants 

 in the drained pots, and the clubs did not attain to so large a 

 size. 



Now there seems to be no reason whatever for assuming that 

 all these plants were first in a state of disease before being at- 

 tacked by the Flasmodiophora. Indeed, it was quite evident 

 that the strongest and healthiest plants were the most favourable 

 to the full development of the fungus. The tissues of a small 

 and feeble plant are speedily disrupted, the cells are choked 



