262 Varietäten, etc. — Physiologie. 



trees are making their most rapid growth, and should be in their 

 most susceptible condition for infection. The trees were well cared 

 for and made rapid growth during the period the experiments were 

 in progress, and hence were in favorable condition for the deve- 

 lopment of the disease. 



Among the great many species of the genus Prunus, that gives 

 a Wide ränge for investigation because of the large number of 

 species and varieties, are three hosts that showed always negative 

 results: P. pumila, P. ilicifolia and P. Caroliniana. The first one, 

 grafted on peach stock, made rapid growth, but never showed the 

 least indication of gall formation; the other ones were on their 

 own roots. 



In P. domestica the writer found three resistant varieties: the 

 German Prune, that gave in 240 inoculations 24 positive results, 

 the Italian Prune (Fellenberg) with 17 positive results in 127 in- 

 oculations and Green gage (Reine Claude). Among the varieties of 

 P. cerasifem, the Myrobalan tree, a very susceptible species with 

 great galls, there is one variety, P. cerasifera var. Planteviensis, 

 that seems to be resistant, although this resistance should be again 

 determined. The variety known as Golden Beauty, P, hortulana has 

 thus far shown more marked resistance than other varieties of the 

 species thus far tested. P. Besseyi, closely related to P. pumila, 

 also Shows considerable resistance, as also the damson, P. insititia 

 and the apricot Mikado, variety of P. Armeniaca. 



M. J. Sirks (Wageningen). 



Willis, J. C, The Endemie Flora of Ceylon, with refe- 



rence to Geographical Distribution and Evolution in 



General: A Correction. (Proc. Roy. Soc. Lond. Ser. B. LXXXIX. 



p. 257. 1916.) 



The object of this note is to draw attention to the Omission of 



part of one of the tables in the author's paper (Phil. Trans. B. CCVI. 



p. 307. 1915), but it is shown that this Omission does not affect the 



final result. Agnes Arber (Cambridge). 



Wilson, M., Sex Determination in Mnium hornum. {Ann. Bot. 

 XXIX. p. 433—440. 1 pl. 1915.) 



El. and Em. Marchai, as a result of their work on the Apo- 

 spory and Sexuality of the Mosses, conclude that there is an abso- 

 lute Separation of sex determinants at the reduction division. The 

 present writer describes a case which appears to invalidate such a 

 conclusion. He found an axis of Mnium hornum bearing normal 

 antheridia, bisexual organs and modified archegonia. In this speci- 

 men the antheridia were found to possess six chromosomes, and, 

 since this is the normal gametophytic number, the plant in question 

 cannot have been produced aposporously. It is suggested that sex 

 determination is not bound up with meiosis, but is brought about 

 by metabolic processes which operate in the organism over a con- 

 siderable part of its lifehistory. Agnes Arber (Cambridge). 



Daniel, L., Sur les effets de l'arrosage capillaire continu. 

 (C. R. Acad. Sc. Paris. 2. CLXIII. W 19. p. 525-527. 1916.) 



Gefässe mit weiter Oeffnung, in denen Wollfäden oder 



