NOTES AND ABSTRACTS. 



639 



Red Spider Control. By E. A. McGregor (Jour. Econ. Entom. 

 vii. pp. 324-336 ; August 1914). — The pest in question is known as 

 Tetranychus himaculatus, but whether the same as T. tetanus of Europe 

 is not at all clear. The distribution of the pest is effected by trans- 

 portation by other creatures, actual locomotion, and carriage on 

 small streams of wa^er during heavy rains. Nine hours' submergence 

 in water was found necessary in order to kill the pests. It is active 

 during winter and is generally distributed, attacking about 130 species 

 of plants, including violet, sweet pea, hollyhock, morning-glory, bean, 

 tomato, and DahHa. Sixteen or seventeen generations of red spider 

 occur in the season in S. CaroHna. Adverse weather conditions have 

 some influence in checking the pest, but the main check appears to be 

 imposed by various insects, including a small fly (Arthrocnodax corolina), 

 a bug (Triphteps insidiosus), a ladybird (Stethovus punctum), a lace- 

 wing fly (Chrysopa ocutata), and a thrips (Scolothrips sexmacutata) , 

 besides others of less importance. The best hope of keeping the pest 

 in check by artificial means lies in preventive rather than repressive 

 measures, and of these the destruction of weeds is the most important. 

 Control of violets, choice of the more immune varieties of cultivated 

 plants, wide spacing, perhaps late planting and rotation, are less effective 

 means of deahng with the pest. Among repressive measures are the 

 removal of infested plants, spraying with liver of sulphur (3 lb. to 

 100 gallons), home-made lime-sulphur, paraffin emulsion, resin wash, 

 miscibleoil, miscibleoil and " black leaf " tobacco extract, " sulfocide," 

 and flour paste solution. The necessity of thorough spraying is 

 insisted upon, as only those red spiders are killed which the spray 

 hits.— F. /. C. 



Reproduction in Plants. By John M. Coulter [Bot. Gaz. Iviii. 

 pp. 337-352 ; Oct. 1914). — In this paper the author gives a general 

 resume of plant reproduction in general. The first stage of asexual 

 reproduction is represented by cell-division, the second by spore- 

 formation, and the third by differentiated spore-forming cells. As 

 regards the origin of sex, gametes have been derived from zoospores 

 so reduced in size by successive division as to be incapable of function- 

 ing as spores. There are gametes alike in every visible feature, but 

 as they pair they are physiologically different. Gametes appear in 

 response to unfavourable conditions and represent the closing activity 

 of a plant. The resulting zygote, being formed under unfavourable 

 conditions must remain dormant until better conditions appear ; it 

 may function as a spore or may produce spores. 



Both the more or less elaborate swimming mechanism of the 

 sperm and the large nutritive supply of the egg are non-essential 

 sexual characters. 



" Nor can it be true that gametes are pecuHar in containing the 

 factors of heredity, for these must have been handed down through 

 all the cell generations leading to the gametes." Heredity expresses 



