DISEASES OF THE PLANT. 311 



be sufficient for two acres, the plants of the latter being 

 cut out in the hoeing or singling, while the produce of the 

 former (Swedes) may be allowed to stand as a crop for seed 

 purposes the following year. If a little attention be given 

 when the plants have arrived at maturity, to look the field 

 over and draw out any faulty roots, the produce will 

 generally sustain a good reputation for quality in the 

 market. Turnip seed is looked upon rather as a specu- 

 lative crop, subject to great variation in yield, from the 

 effects of weather, wind, and other injuries, which, of 

 course, if general, affect its market value also. The pro- 

 duce varies greatly according to the season and the variety 

 grown ; it may be taken at 20 to 30 bushels per acre. 



The turnip is not subject to so many diseases as some 

 others of our cultivated plants. Its greatest danger is 

 from the attacks of insects, which visit it at every stage 

 of its growth. Frequently on rich vegetable soils, or 

 where a large proportion of organic manure has been 

 used, we see the young plant exhibiting a very vigorous 

 growth, with leaves of a rank, deep green colour, extremely 

 large and succulent, indicative of an abnormal develop- 

 ment of the top, and a proportionate weakness of the root 

 and general vitality of the plant. Such plants are very 

 liable, Mr. Berkeley tells us, to be attacked by a species 

 of Botrytis (B. parasitica), nearly allied to the potato 

 mould, and scarcely less injurious in its effects. The roots 

 in those plants in which the parasite has effected a lodg- 

 ment are very liable to decay, and a decomposition of the 

 waUs of the spiral vessels is frequently traceable for 

 several inches, being 'always the sure forerunner of 

 complete decay. In many cases, again, where the plants 

 have been cultivated under ordinary conditions, and have 

 sustained their ordinary growth under certain conditions 

 of moisture and temperature, the surface of their leaves is 

 covered more or less with a light mould, so as to give 



