i9Hl current literature 283 



genus now and then becomes enriched suddenly in a new region, 7 new species 

 being added to its list. Among the new species is a Dacrydium, which means 

 more than a new angiospermous species. The ratio of increase in the number 

 of species as the flora of the tropics becomes known is so great that a new 

 census of the plant kingdom is called for, as the old enumerations, so often 

 quoted in textbooks, are wide of the mark. — J. M. C. 



Syncotyly and schizocotyly. — Compton 8 has made a somewhat extensive 

 investigation of dicotyledonous seedlings with a single cotyledon, and also of 

 those with more than two cotyledons. The terminology of the title indicates 

 his belief that the single cotyledon of a dicotyledonous seedling is the equiva- 

 lent of two fused cotyledons; and that extra cotyledons represent a splitting 

 of cotyledons. 



The conclusions in reference to syncotyly are in substance as follows: 

 syncotyly occurs in a great number of species, normally or " teratologically " ; 

 in species with albuminous seeds syncotyly usually gives rise to a symmetrical 

 cotyledonary tube, the reason probably being "the homogeneity of the sur- 

 roundings of the embryo before germination"; in species with exalbuminous 

 seeds syncotyly is usually asymmetrical, the cotyledons uniting along one edge 

 only, the suggested reason being "the asymmetry of its [embryo] environment, 

 which produces accumbency and other irregularities." 



The study of schizocotyly is made the basis of a discussion as to the primi- 

 tive condition of cotyledony. Arguments have been advanced for both 

 dicotyledony and polycotyledony as the primitive condition. The author's 

 judgment inclines to dicotyledony as the primitive condition. If this historical 

 question must be settled, it will probably have to await the discovery of the 

 embryos of Cycadofilicales.— J. M. C. 



Tyloses. — The extensive collections of the Forest Products Laboratory 

 have enabled Miss Gerry to undertake a survey of the occurrence of tyloses. 9 

 Of the 45 genera of hardwoods examined, 24 are found to contain tyloses. 

 These proliferous growths into the vessels naturally reach their most marked 

 development in ring-porous woods, such as oak, although in this genus black 

 oaks rarely show tyloses, while white oaks show abundant evidences. Woods 

 in which parenchyma surrounds the vessels show the best development of 

 tyloses, though the proximity of medullary rays to vessels is also a factor. 

 Contrary to previous accounts, Miss Gerry finds tyloses in the sap wood of 

 all species in which they occur in the heart wood, and she produces photographs 

 of hickory which illustrate the point. With respect to soft woods, Pinus is 

 the only genus in which true tyloses have been found, and here they are held 



Compton 



Ann. 



Botany 27:793-821. Jigs. 41. 1913. 



9 Gerry, E., Tyloses; their occurrence and practical significance in some Ameri- 

 can woods. Jour. Agric. Research 1:445-470. pis. 52-59. 19x4. 





