AGRTCULTUKAL BOTANY. 221 



AGRICULTURAL BOTANY. 



Report of the botanist, (J. E. Stone and N. F. Monaman (Massficlnisctts 

 Std. h'i)t. 190.'), pij. JI.')-I'i.j). — Notes are given on a number of diseases tbat bave 

 iieen under observation. The long period of dry weather rendered many plants 

 free from fungus diseases, but. on tbe other hand, tbe conditions were favorable 

 for the outbreaI< of otbers. The downy mildew of tbe tomato, potato rot, and 

 cuoumber and melon I)ligbt are briefly noted, after wbich tbe effect of sun scald, 

 leaf scorch of conifers and other evergreens, winterkilling, etc., are described. 



An account is given of some investigations carried on to determine tbe rela- 

 tion between soil aeration and germination and growtli. In tbese experiments 

 air wa.s forced tbrough tbe soil, and lettuce seed, wbich is quite susceptible to 

 aeration, was planted in tbe different boxes-. From tbe results tabulated it is 

 sbown tbat a considerably larger proportion of tbe seed germinated in the 

 aerated box tban in tbe unaerated one. 



A comparison of sterilized loam and sterilized subsoil was made, 8 pots 

 being used, 4 containing loam and 4 subsoil; of these 2 each of the loam and 

 subsoil were sterilized, and the remaining pots were left uiisterilized as 

 cbecks. After sterilization soy beans were planted, and in the sterilized loam 

 tbere was an increase of 14 per cent in the germinations, wbile in the sterilized 

 sub.soil there was a loss of TjI.T percent. No explanation of this pheuomenon 

 is offered, but it shows tbat extreme precautions are necessary in drawing de- 

 ductions from experiments in wbich tbe soil is sterilized. 



Tbe influence of soil sterilization on the germination of old seed was tested, 

 tbe object being to ascertain tbe degree of acceleration which would result from 

 seed planted in sterilized soil. Seventeen lots of seed were planted in sterilized 

 soil and an equal number in unsterilized soil. The germinations were counted, 

 and showed a positive gain in the germination of seed sown in ^sterilized soil. 

 Marked differences were obtained from different kinds of seed, tomatoes re- 

 sponding but little, if any, to this metbod of treatment. Tbe cause of the 

 variation in different species is unknown. 



In attempting to ascertain tbe causes underlying tbe effects off st^rilized soil 

 on seed germination mentioned above, tbe autbors carried on a series of experi- 

 ments in wbich soil decoctions were used to water the seed. The results indi- 

 cate tbat the acceleration and increased germinating capacity of sterilized soil 

 niay have a chemical explanation. Fndoubtedly the driving out of the ga.ses 

 and the subsequent absorption and renewal of fresh oxygen in sterilizing prac- 

 tices act beneficially to the soil and induce the seed to germinate more (luickly. 

 Sterilized subsoil, or soil lacking in humus, has the same effect on germination 

 as sterilized loam rich in organic matter, but it inhibits growth to a large extent, 

 differing markedly in this respect. It appears from these experiments that a 

 considerable amount of humus is necessary in soils in order that they may be 

 materially benefited by sterilization. 



The results of germination exi)eriments to test the relative value of light and 

 heavy seeds are given. The general conclusion is drawn tbat with many kinds 

 of garden seed it is best to separate the seed and discard all but tbe large, well- 

 developed, mature, and heavy seed. 



Tbe occurrence of asparagus rust during the season is discussed, this disease 

 having been iiarticularly troublesome in many parts of Massachusetts as tbe 

 result of the extremely dry summer. Cultural methods are said to have given 

 beneficial results in keeping this disease in check, and weekly cultivation com- 

 bined with judicious fertilization has proved verj^ satisfactory. The autbors 

 JH'lieve that the i)ractice of burning the old asparagus brush in tbe fall is, by 

 destroying a large number of tcleutospores, an elhcient metbod of control. 



