546 Cytologie. — Descendenz etc.. — Morphologie. — Physiologie. 



Leavitt, R. G., The Defenses oi the Cockspur Thorn. 

 (Plant World. Vol. VIII. p. 239—245. fig. 49—50. Oc- 

 tobre 1905.) 



Thorns in Craetegus Crus-galli are modified branches and 

 the majority — 119 in 172 — point downwards, vvhich is con- 

 trary to expected effect of geotropism. To be explained as 

 protective device against herbivorous animals which use tongue 

 in browsing. M. E. Latham (New York). 



Clute, W. A, The Defenses of the Cockspur Thorn: 

 another Interpretation. (Plant World. Vol. VIII. 

 p. 303—305. fig. 60. Dec. 1905.) 



Refutes the conclusions of Leavitt, citing instances where 

 the thorns are entirely ineffective for the supposed protection, 

 and also points out that they are produced as freely on the 

 Upper as on the lower branches. M. E. Latham (New York). 



Morgan, T. H., The Assumed Purity of the Germ Cells 

 in Mendelian Results. (Science. N. S. Vol. XXII. 

 p. 877—879. Dec. 29, 1905.) 



Offers a new set of Mendelian formulae with a new 

 conception of dominance and recessiveness. The idea brings 

 into question the assumption of the so-called purity of the 

 germ cells. Purity only means dominance over latency. Domi- 

 nance over recessiveness follows a different rule, namely the 

 rule of alternation or of contrasted gametes. 



H. M. Richards (New York). 



HORI, S., Abnormes Wachsthum bei Canabis satlva L. 



(Zeitschr. für Pflanzenkrankh. Bd. XVI. 1906. p. 1-2.) 



Verf. weist auf ein Auftreten von abnorm kleinen und dicken, blass- 

 gelben, meist gekräuselten Blättern im oberen Theile von im Glashaus culti- 

 virten weiblichen Hanfpflanzen hin, eine Erscheinung die durch Blattläuse 

 hervorgerufen wird. Als bemerkenswerth wird ein eigenthümlicher 

 Pfeffermünzgeruch der missgebildeten Blätter angeführt. — Aehnliche 

 durch Aphiden hervorgerufene Verunstaltungen der Blätter kommen be- 

 kanntlich an sehr vielen Pflanzen vor und sind auch vom Hanf bereits 

 bekannt. Laubert (Berlin-Steglitz). 



SCHNECK, J., Fasciation in the Cherry. (Plant World. 

 Vol. VIII. p. 35—36. Fig. 14. Feb. 1905.) 



In Order to define fasciation as „the coalescence of some 

 or all of the growing points of a plant or branch", two in- 

 stances are cited of fasciation in Prunus serotina where com- 

 plete adhesion had taken place between branches. 



M. E. Latham (New York). 



Balfour, J. B., Physiological Drought in Relation to 

 Gardening. (Plant World. Vol. VIII. p. 1-5. fanuary 

 1905.) 



