1898J NOTES AND COMMENTS 375 



that the colours of flowers are not a source of attraction for 

 insects, 



POLYEM BRYONY IN SeED-PLANTS 



By a communication to the Botanical Gazette (April) Mr W. F. 

 Ganong adds another to the already somewhat numerous instances 

 of the production of more tlian one embryo in the embryo-sac. The 

 case is that of the prickly pear (Opuntia vulgaris). The plants had 

 been growing and flowering luxuriantly in the Botanic Garden of 

 Smith College, Northampton, Mass., for at least four years, and set 

 seed each year in great abundance. About half of the seeds when 

 sown produced more than one seedling, and there was the greatest 

 variation in the number, size, and degree of union with one another 

 of the seedlings. Investigation showed that the embryos originate 

 as described by Strasburger for Fwiikia, and as has since been 

 shown to be the usual method where polyembryony occurs, from the 

 cells of the nucellus, the original tissue of the ovule. The egg-cell 

 shrivelled and disappeared. The question arises as to the signifi- 

 cance of polyembryony. The writer argues that it is too distinct and 

 elaborate a process to be explained as mere budding, as Strasburger 

 and Pfeff'er suggest, and that the variety in the place of origin of 

 the embryos from egg-cell, synergids, antipodal cells, or nucellus, 

 preclude the idea of its being a relic of some older condition, or a 

 case of apogamy. On the other hand, it may be the beginning of 

 something new. "Its origin in several distinct groups and by several 

 distinct methods seems to imply that there is some virtue in the 

 development of the extra embryos, and that their appearance is con- 

 trolled by that influence, whatever it may be, which is much more 

 powerful than mere morphological inertia, and which elsewhere forms 

 new structures from the most different morphological origins." Its 

 independent appearance in distinct groups may be compared with 

 the appearance of heterospory. 



Vaccination in Japan 



While vaccination is under the consideration of our legislators, it 

 may be interesting to note that it is compulsory in Japan, and 

 that re-vaccination must be undergone every five years. We 

 learn from the Revue Scientijique that the process was intro- 

 duced into that country in 1849 by a Dutch physician, Nagayo 

 (which seems to us less of a Dutch than a Japanese name), 

 but was first made official in 1871 by the establishment of a 

 vaccination office in connection with the Medical College of the 

 University of Tokyo. The lymph used at that time was derived 

 from the human vaccine imported by Mohnike. But in 1879 

 a commission was sent to Europe to study the subject, and on 



