592 s KM MARY OF CURRENT RESEARCHES RELATING TO 



phenomenon entirely independent of exterior circumstances, and in 



Antirrhinum is a Mendelian character recessive to the normal. Both 

 the peloric and zygomorphic flowers of Antirrhinum, and the peloric 

 isomerous flowers of Linaria, are isologous and independent of gamo- 

 gernmy. The fundamental cause of difference in development has not 

 yet been discovered, but is probably to be found in that theory accord- 

 ing to which the development of the organs depends upon the presence 

 of some special chemical compound in the tissues of the plant. 



General. 



Modification by Crossing.* — R. R. Gates publishes the results of 

 some experiments made with the purpose of ascertaining the extent to 

 which it is possible to modify the characters of plants by crossing. In 

 hybrids produced by crossing Oenothera rubricalyx and CE. grandiflora 

 the characters of the foliage form a continuous series in which blend- 

 ing and fractionation of character is the rule. The pigmentation of 

 the flower of CE. rubricalyx, being the result of a dominant unit- 

 character, affords important evidence, and it is found that " plants 

 which are intermediate in pigmentation breed true, . . . and that the 

 degree of pigmentation in the parent is adhered to in the offspring." 



" In back-crosses of these hybrids with CE. rubricalyx the pigmenta- 

 tion is much intensified, and with CE. grandiflora much diluted. The 

 author thinks that this may be explained by assuming that the " grandi- 

 flora " chromosomes may " exert a mass-effect in inhibiting the influence 

 of the R chromosome," i.e. the chromosome to whose influence the red 

 colouration is due. In any case there is no doubt that the R character 

 is permanently diluted by crossing with the " grandiflora " type, and as 

 the dilution "increases, the pigmentation becomes discontinuous and 

 appears in spots or patches. 



CRYPTOGAMS. 



Pteridophyta- 



(By A. Gepp, M.A. F.L.S.) 



Secretory Tissues of Marattiacese.* — C. West, writing on the 

 structure and development of the secretory tissues of the Marattiacese, 

 says that lysigenous mucilage-canals were found in every genus and 

 species of Marattiacere examined. They are usually protogenetic, but 

 occasionally hysterogenetic (e.g. petiole of Kaulfussia sesculifolia and root 

 of Angiopteris evecta). In the petiole of A. evecta the mucilage-canals 

 may be lysigenous or schizo- lysigenous. Tannin-cells are widely dis- 

 tributed through the sporophytic tissues of the Marattiacese ; they occur 

 either as isolated tannin-sacs, or grouped together in regular or irregular 

 series. Lysigenous tannin-ducts are formed by the solution of the septa 

 between adjacent tannin-cells. 



* Amer. Nat., xlix. (1915) pp. 562-9. 



t Ann. Bot., xxix. (1915) pp. 409-22 (1 pi. and figs.). 



