March, 1909.] 



Plant Sanitation. 



and regular plans should be made for 

 treating them on these lines rather than 

 continuing the neglectful method of 

 leaving naked heaps in the field which 

 commonly prevails. At present the 

 disease does not seem to gather much 

 headway, and this is probably due to 

 natural checks upon its spread. The 

 principal destruction by it appears to 

 occur on poorly cultivated or inferior- 

 soils. Many planters contend that it is 

 not present, but there are few estates 

 on wbich it cannot be found. It is not 

 recognisable to the naked eye uutil the 

 result of its mischief is evident in the 

 death of the pod, branch and root, but 

 nevertheless, it can be found by the 

 expert in unsuspected places v/here un- 

 favourable seasons would cause it to 

 show itself with destructive effect, and 

 unless a proper watch is kept upon its 

 action and progress, together with that 

 of the equally insidious Canker fungi 

 or Necirias (from which, however, it is 

 absolutely distinct), it is possible that 

 it may become a very serious matter to 

 that section of the planting community 

 who are dilatory and unwilling to adopt 

 hygienic measures, and are generally 

 neglectful in the management of their 

 estates. At the same time there is every 

 reason to hope that, given clean, well 

 manured, well drained and well culti- 

 vated estates, where hygienic methods 

 obtain, planters have no need to become 

 alarmed. One fact is certain, as seen in 

 our last dry and unfavourable season. 

 Those estates where bad pruning, bad 

 drainage, etc., prevail and where "pick, 

 pick, and keep on picking" is the first 

 order of the day, will most assuredly be 

 those which will afford no encourage 

 ment to the planter. It may be men- 

 tioned that Diplodia, though better 

 known than Lasiodiplodia, is still placed 

 by some authors also among Fungi 

 imperfecta and it is to be understood 

 that there is much more to be learned 

 about its history and habits than has 

 yet appeared. Since commencing this 

 article we have seen Diplodia on the 

 Grape vine and on grains of Corn, and 

 literature shows that in Europe species 

 of it attack the Holly, Lilac, Chestnut, 

 Mulberry and various conifers. It is 

 also reported to attack the Avocado 

 pear, the Sugar cane and the Mango. — 

 Agricultural Society oj Trinidad, Vol. 

 VIII., Pt. 11, November, 1908. 



DEVELOPMENT OP DISEASE- 

 RESISTANT VARIETIES 

 OP PLANTS. 



By H. S. Jackson, Newark, Del. 



{Concluded from page 168.) 



An interesting application of disease- 

 resistant varieties illustrating one of 

 the uses to which such varieties may be 

 put is seen in the American grape wines 

 used as stocks on which to graft the 

 European wine grapes. Many years ago 

 an American viue insect known as the 

 Phylloxera was introduced into Europe 

 where it spread with great rapidity. 

 Its most serious damage was done by 

 its ravages on the roots. It soon wiped 

 out many of the largest vineyards of 

 Prance and other European countries. 

 Por a time it looked as though the whole 

 vine industry of Europe was threatened. 

 The matter was thoroughly investi- 

 gated, and it gradually became known 

 that certain American vines were com- 

 paratively resistant to the attacks of 

 this insect- Someone conceived the 

 idea of grafting European varieties on 

 American stocks. After many failures 

 it Avas found that if certain strains of 

 Vilis riparia and V. rupeslris, both 

 native American grapes, were used as 

 stocks, that very little trouble was ex- 

 perienced from the Phylloxera. In Cali- 

 fornia gr owers of European grapes have 

 had the same trouble with practically 

 the same results as regards successful 

 treatment. 



In Prance great success has been met 

 with by Millardet in hybridizing the 

 American with European grapes for the 

 purpose of uniting the Phylloxera-resist- 

 ing qualities of the former with the 

 wine-producing qualities of the latter. 

 He has also succeeded in combining the 

 above qualities with resistance to the 

 downy mildew. 



This brings us to the question— Is it 

 possible to obtain disease resistance in 

 an individual of one variety or species 

 by grafting on an individual of another 

 variety or species ? There is some 

 evideuce in the affirmative, but the 

 question is at most a disputed one. It 

 is worthy of careful investigation. If 

 such be the case, would the induced 

 immunity be transmitted to offspring 

 or to cuttings ? If so, then we must 

 admit the existence of graft hybrids, 

 which most plant-breeders are not 

 willing to do. 



While comparatively little has really 

 been done in the actual development of 

 disease-resistant varieties, enough has 

 been accomplished to indicate the possi- 



