1909] CURRENT LITERATURE 81 



least, several characters must reside in one chromosome. The characters must 

 then be confined to separate particles or corpuscles of the chromosomes, and an 

 interchange of homologous particles according to chance during maturation would 

 give the Mendelian combinations. Many observers, including Strasburger, 

 Rosenberg, Allen, and Schreiner, have described such an interchange of 

 particles; but Gregoire's conclusion, which he has emphasized before, is that 

 nothing in the observations of the ' nuclear reticulum, the somatic spirem, or 

 the heterotypic spirem justifies the admission of representative particles, chromatic 

 or achromatic. The "chromomeres" observed particularly in the heterotypic 

 spirem, he considers not as autonomous granules imbedded in a substratum, but 

 merely as a substratum impregnated with chromatic material and rather regularly 

 alveolated, giving the appearance of a single or double row of "chromomeres." 

 Grf.goire further denies that there is an interchange of particles between 

 the parallel filaments in the double spirem stage, such as various cytologists have 

 described. These two facts, namely, the presence of autonomous particles and 

 their free interchange at some time during the reduction processes, would appear 

 to be essential to a cytological basis for Mendelian phenomena.— R. R. Gates. 



Extra-floral nectaries and "myrmecophily." — To many who have held the 

 untenable view that plant structures are necessarily useful, extra-floral nectaries 

 have been a stumbling-block. Nieuwenhuis-Uexkull 9 has made an exhaus- 

 tive study of the extra-floral nectaries of 100 species of plants growing at Buiten- 

 zorg, and it may be said that these studies are of great importance because they 

 show conclusively that we know nothing concerning the advantage of these peculiar 

 organs. There is an admirable critical review of the treatises that consider extra- 

 floral nectaries, beginning with Hall's study in 1762. The term extra-floral 

 nectary was first employed by Caspary in 1848, who rather inclined toward 

 iebig's theory that they are of value to plants as a means of excreting sugar 

 * en present in excess. The classic study of these organs is Delpino's treatise 

 jssued in i8 74) j n which the term ex tra-nuptial nectaries is employed, and the 

 1 Ca advan «d that the sugar they secrete attracts ants; these insects in turn are 

 supposed to defend such plants against their enemies. Simultaneously with 

 ^lpixo, Belt proposed a similar theory for Acacia sphaerocephala, and from 

 mec nhS ^^ recentl y bota nists have generally believed in the existence of myr- 

 bee CO piles, or ant-loving plants. Among the supporters of myrmecophily have 

 remdelr^' FRm MttLLER > Trelease, and Schimper. Bonnier (1878) 

 incM i aU nectaries as su 8 ar reservoirs, any other function being thought quite 

 "unb-M and KERNER ( i8 7 8 ) regarded extra-floral nectaries as protective against 

 meco'h M gUeStS *" Be g innin g with th e skeptical attitude taken toward myr- 

 P "y by von Ihering in 1894, there have been critical contributions by 



*heidun EmVENHU1S V ° N Uexk ull-Guldenbandt, M., Extraflorale Zuckeraus- 



gen und Ameisenschutz. Ann. Jard. Bot. Buit. II. 6:195-327- I0O 7- 



