( 49 ) 



plots bv I)eanhe(l<;-es and lliat lliesc liedjes coiisisled |)arlly of scarlet- 

 I'liimcrs [Plmsi'oliis cocc/iieiis = /%. /////////A'yv/xj and |»ai-ll\- of •'ciirvcMJ- 

 iH'ak" (a \ai'iely of French heajis Pluiscohis i-nhjaris Swi '). 



Oil account of their height these plants were cojisidci-ed elfectiNc 

 as windscreens, 'i'obaceo leaves namely, hy iheii- laruc sin-face as 

 well as hy their tender striictiire, cannot \ery well stand aii'-ciirrents, 

 which is proved hy the fact that the scoiirini>' or riilihinu' of two 

 lea\'es against each other by the wind, may cause discoloured spots, 

 bruising of the tissues and even loss of substance. 



Though the method of protecting the tobaccoplant against wind 

 had evidently been well chosen, yet the growt^rs themselves had 

 noticed that it w'as wrong to use two different kinds of I^IhiscvIhs, 

 because diseased tobaccoplants are much more frequent within hedges 

 of scarlet-runners than of F'rench beans. Experts are certainly riglit 

 in their opinion that the reason of this is that scarlet-runners retain 

 their leaves much longer than French beans. The latter begin (o 

 lose their leaves alread}^ in September and October, when the season 

 can already be rather damp, whereas the scarlet-ruimers sho\v no 

 sign of it yet then. Hence the soaked soil as well as the damp plants 

 can much better be dried by the wind within the hedges of French 

 beans than of scarlet-rumiers. Accordingly the "rot" is in (lain|t years 

 always much stronger inside the leafed than inside the leafless hedges. 



Another drawdiack of scarlet-runners is that their flow^er-clusters 

 have not yet fallen off in September and OctoI)er, so that, after 

 having died, they not unfrequenth^ droj) down on the tabaccoplants 

 and soaked through, remain hanging in the axils and in other places, 

 where like w^et sponges they foster the germination of conidia or spores. 



In a visit to the tal)accofields of Mr. K. van Os at Amerongen 

 on Sept. 27, 1902, many plajits were foiuHl sullering tVom "rot". 

 As such the growlers considered specimens with limp, sli[)pery leaves 

 and Avith stems ha\ing discoloured stains. This was siippoiMcd by 

 the experience that such leaves and stems i)ossess very infectious 

 properties and that a single diseased leaf, cari-ied to the di'ying-shed 

 under a big heap on a wheelbarrow, can in one night easily infect 

 some fifty others. Any precise idea of the agent here at work, was 

 not found however among the ex|)erts, so that the only means of 



1) The tobacco-growers themselves informed us that hedges ol' l)eans, especially 

 of scarlet-runners and "curved-beaks" as windscreens, have l)eeii in use on 

 tobacco fields as far back as can be remembered, in accordance with this they 

 are mentioned by the lale Prof, van Hall on page <i(J and 01 of his "Landiiuis- 

 houdkundige Flora" dating from 1855. 



4 



Proceedings Royal Acad. Amsterdam. Vol. VI. 



