SPERM ATOPHYTES— GYM NOSPERMS 



345 



neck and upper part of the archegonium with a needle, pressing, and 

 at the same time drawing, the needle away, so as to pull the young 

 embryo out. Some of the embryos will be broken, but by care- 

 ful manipulation more 

 than half should be en- 

 tirely uninjured. Fix in 

 formalin (5 per cent in 

 water) , stain in Delafield's 

 haematoxylin, transfer to 

 10 per cent glycerin, and 

 continue with the Vene- 

 tian turpentine method. 

 A preparation made in 

 this way is shown in the 

 photomicrograph (Fig. 

 121). 



These stages, and all 

 subsequent stages, are 

 easily cut in paraffin with- 

 out removing the embryo 

 from the endosperm. Cut 

 a thin slab from opposite 

 sides of the endosperm, 

 fix in chromo-acetic acid, 

 with or without osmic 

 acid, imbed in paraffin, 

 and stain in safranin and 

 gentian violet. This will 

 give a good view of the 

 abundant starch and 

 other food stuff, and at 

 the same time will bring 

 out sharply the cell walls 

 of the embryo. 



Fig. 121. — Piiius banksiana: photomicrograph of 

 young embryos teased out by the method described in 

 the text; from a preparation by Dr. J. T. Buchholz; 

 Cramer contrast plate; 16-mm. objective; no ocular or 

 Abbe condenser; camera bellows, 75 cm.; safranin filter; 

 arc light; exposure, 17 seconds. Negative by Miss Ethel 

 Thomas. X54. 



GYMNOSPERMS— GNETALES 



Of the three peculiar genera belonging to this order only one. 

 Ephedra, occurs in the United States. Welwitschia is found only in 

 Damaraland, South Africa, and Gnetum is tropical and subtropical. 



