Pflanzenkrankheiten. — Floristik etc. 525 



Morris, R. T., Chestnut blight resistance. (Journ. of Here- 

 dit5^ V. p. 26-29. 1914.) 



The present paper gives the results of the writers experience 

 and observations in growing chestnuts and their resistance to bark 

 disease. When it became evident, that the American chestnut trees 

 on his place were seriously menaced, the question of finding blight- 

 resistant individuals among species and varieties canie up and the 

 writer proceeded to add to his coUection various species and varieties 

 until it included twenty-six different kinds, among these kinds spe- 

 cies were as follows: American sweet chestnut [Castanea ainericana)^ 

 bush chinquapin [Castanea piunila), tree ohmo^v.di'pixi {Castanea piiniila 

 arhorifonnis) , alder-leaf chestnut [Castanea alnifolia), evergreen chest- 

 nut [Castanopsis chrysophylla or C. senipeyvi)'e}is). In addition to these 

 American species of chestnut there were two specimens of the Chinese 

 Castanea mollissima and many specimens of species not determined 

 by the writer from England, France, Italy, China, Korea and 

 Japan. Very resistant showed to be Castaiiea alnifolia and Castanea 

 mollissima; none of the trees belonging to these species has blighted. 

 In his breeding experiments in order to obtain hybrid chestnuts, 

 which would be resistant to blight, the writer made various com- 

 binations between staminate and pistillate flowers of Castanea alni- 

 folia, C. pumila and C. mollissima. The most promising hybrid for 

 timber purposes would presumably be one between C. mollissima 

 and C. pumila arboriforniis. 



When making hybrids between various species of chestnuts, 

 the writer incidentally determined that parthenogenesis apparently 

 occurs among the Casta)ieas. The parthenogenetic nuts showed some 

 peculiar features; freaks, cotjdedons protruding through the involucre 

 before the nuts were fully developed showed a trifle of chloroph^il 

 coloration ; the disparit}'^ in size between shoots which grew from 

 them in the following year, some becoming much larger and some 

 remaining smaller than chinquapins from normal gametes. Inciden- 

 tally the writer states that similar experiments were tried with 

 Juglans cinerea, Hicoria ovata, H. glahva and H. minima and all of 

 these apparently developed nuts b}'- parthenogenesis, /z/^/rt«s a^er^ö 

 treely, and the three hickories sparingly. M. J. Sirks (Haarlem). 



Bazhanov, S., Weeds on the Buzuluk Experiment Field 

 (Samara prov.) and in the vicinity. (Bull. appl. Bot. VIII, 

 p. 276—293. 1915. Russian and english.) 



Owing to the presence of weed seeds in the soil, the total amount 

 of weeds in the harvest of wheat on the Buzuluk Experiment Field 

 showed a marked increase, in relation to the percentage of weed- 

 seeds among the sown grains. Therefore the writer has made some 

 analyzations of the soil samples, taken from different parts of the 

 experimental field, the results of which are published in this paper. 



It was observed that the distributions of weed seeds attains the 

 rate of about 3000 seeds in the soil per 1 sq. metre of seed bed, 2 

 inches deep, what makes 34.000.000 seeds perl hectarand 160.000.000 

 per the same area but 8 inch deep. These seeds belong mostly to 

 Convolvitlus arvensis, Dracocephaliim thymißoviim, Ceratocarpus 

 arenarius, Triticum. repens, T. intermedium, Kochia sedoides a. o. 

 Besides the examinations of the soil samples, the field crop of the 

 wheat has also been investigated by the author. There have been 



