ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 483 



embryo ; it is in the central tissue alone, derived from the preliminary 

 formation of vesicles, that the archegones are developed. In the division 

 into vegetative and generative portions we have a form of endosperm at 

 present known ouly in Gnetum and Sequoia among Gymnosperms. 



Embryogeny of Silphium.* — In a general account of the structure 

 and biology of this genus of Compositae, Mr. W. D. Merrell has the fol- 

 lowing notes on its embryogeny. When the male nuclei enter the 

 embryo-sac, they have (in three of the species examined) a sinuous or 

 spiral form, a phenomenon not before recorded in Dicotyledons ; but 

 tinally the spiral form is lost, the nucleus being merely slightly bent. 

 The pollen-tube enters the embryo-sac just below the edge of the nucellar 

 cap. Impregnation may be accomplished without the previous dis- 

 organisation of either of the synergids. The division of the definitive 

 nucleus precedes that of the oosphere. The polar nuclei fuse before im- 

 pregnation, and the definitive nucleus lies near the egg-apparatus. The 

 antipodals are arranged in a row, as is usual in Compositae. The nuclei 

 of the pollen-mother-cells show a well-marked synapsis stage, and pass 

 quickly from this to the formation of the spindles for the first division. 

 In the equatorial plates of this spindle the reduced number of chromo- 

 somes, eight, was repeatedly counted. The second division follows 

 immediately after the first. 



Embryogeny of Lathrgea.f — Prof. "R. Chodat and M. C. Bernard 

 describe the following speciality in the development of the embryo of 

 Lathrsea squamaria. From the chalazal cell of the two resulting from 

 the division of the secondary nucleus there springs a " haustorium " im- 

 mediately beneath the endosperm-cells, in an equatorial direction ; it is 

 thick, and grows in length until it reaches the raphe. The starch contained 

 in the integument disappears when in contact with it. A second haus- 

 torium is then formed at the micropyle from one of the upper endosperm 

 cells ; it is thin at its base, but swells out to a gut-like form as it 

 traverses the integument to reach the placenta. Within the tube a 

 multiplication of nuclei takes place. The embryo-sac of Lathrsea 

 squamaria contains therefore two " haustoria," one equatorial, the other 

 micropylar. 



Embryo-sac of Saururus.J — According to Mr. D. S. Johnson, the 

 primary archesporial cell divides, in Saururus cernuus (nearly allied to 

 Piperaceae), into an upper tapetal and a definitive archesporial cell, which 

 forms three potential megaspores, the lower one becoming functional, and 

 developing the usual 7-nucleated embryo-?ac, which becomes flask- 

 shaped. The antipodals soon become indistinguishable, and endosperm 

 forms in the neck of the flask before any change appears in the oosphere. 



Development of the Pollen-grain in Symplocarpus and Peltandra.§ 

 —Mr. B. M. Duggar has studied the development of the pollen-grain in 

 Symplocarpus fcetidus and Peltandra undulata, both belonging to the 

 Aroidese. Among the points of interest are the following. During the 

 initiation of the spirem stage the nucleole has a distinctly budded form, 

 sometimes consisting of a single large body and of one or two smaller 



* Bot. Gazette, xxix. (1900) pp. 99-133 (8 pis.). 



t Arch. Sci. Phya. et Nat., ix. (1900) pp. 92-4. 



J Bot. Gazette, xxix. (1900) p. 13(5. § Tom. cit., pp. 81-98 (2 pie.). 



