172 Morphologie und Teratologie. 



cell, probably the tapetal cell, is cut off on the outer side. The 

 inner cell then deveiopes directly into the embryo-sac. Its deve- 

 lopement up to the time of fertilisation is normal; the lateral tissue 

 of the nucellus becomes almost completely destroyed, but a con- 

 spicuous cap remains at the apex of the embryo-sac. At fertili- 

 sation the pollen tube pushes down between the cells of the nucellar 

 cap and apparently penetrates one of the synergidae. The two gene- 

 rative nuclei are discharged into the embryo-sac, whilst the tube 

 nucleus probably remains in the pollen tube: fusion of the sexual 

 nuclei or of the polar nucleus and the second male nucleus was not 

 Seen. Each division of the endosperm nucleus is accompanied by 

 the formation of a division wall between the daughter nuclei. The 

 primary endosperm nucleus lies at the base of the sac and by its 

 division forms the two primary endosperm cells. The lower of these 

 is small and fiattened and only divides verticaily, resulting at first 

 in four cells; the upper gives rise to the major part of the endo- 

 sperm. The basal tissue is sharply separated from the rest by its 

 appearance. After fertilisation the ovum becomes divided by trans- 

 verse walls into three cells, the lowest forming a rudimentary sus- 

 pensor. Later the embryo consists of a spherical mass of tissue. 

 The lateral stem apex becomes completevely enclosed by the sheath- 

 like base of the cotyledon. The embryo is well advanced in the 

 ripe seed but some endosperm also persists. 



The young ovule of Neplithytis is very massive, due to the 

 great developement of the basal region and integuments. The sporo- 

 genous cells are very variable in number and several embryo-sacs 

 generally begin to develope, but probably one sac finally crowds 

 out the others. The developement is extremely variable and it is 

 suggested that the cell complex found in the nucellus may be due 

 to the combination of two or more primary embryo-sacs : in no case 

 did the mature embryo-sac show the typical structure. The most 

 significant variations are: a) Presence of several embryo-sacs or of 

 one sac divided up by septa. b) Irregularity in the number of 

 nuclei, from four to fifteen being found. c) Occasional multiple 

 nuclear fusions. d) Less marked polarity of the sac; definite syner- 

 gidae may be wanting and antipodal cells may be entirely absent. 

 In some cases the pollen-tube seemed to penetrate the Single syner- 

 gid present. The position of the embryo is variable and it may 

 occur at the side or base of the embryo-sac. No suspensor is pre- 

 sent. Later on the embryo consists of a spherical mass of tissue. 

 The endosperm developement varies with the structure of the 

 embryo-sac. The latter shows a bend near the middle and the lower 

 cells have much denser cytoplasm than the upper. 



The author concludes that the primitive type of flower in the 

 Araceae is found where the flowers are unisexual, the pistillate 

 flower having a single carpel and solitary basal ovule; the more 

 specialised forms possess two or more carpels. The occurrence of 

 a group of sporogenous cells in Arisema, Aglaonema, and Nepli- 

 thytis may be a primitive characteristic. The variations in structure 

 in the embryo-sac of Neplithytis and Aglaonema commutatum show 

 a resemblance to species of Peperomio, but they may perhaps be 

 pathological. In all investigated species the endosperm is septate 

 from the first and soon fills the embryo-sac. The Araceae are a 

 primitive family of the Monocotyledons and may possibly show a con- 

 nection with the lower Dicotyledons through forms like Peperomia. 



M. Wilson (Glasgow). 



