Reproductive Structures of Vascular Plants 177 



Slides of the caryopsis and embryo ol niai/e are not difFicult to 

 make if the fundamentals outlined in the earlier chapters are ob- 

 served. Consult the bulletins of agricultiual colleges for the methods 

 of making hand pollinations. Collect the ears at the desired intervals 

 after pollination. Remove the husks carefully and trim away two 

 rows of kernels without damaging the adjacent rows. With a thin, 

 sharp scalpel cut oft" the intact kernels close to the cob and drop them 

 into a Petri dish of water. Lay a kernel, with the germ upward, on a 

 sheet of wet paper, remove chaff from the base and trim a longitu- 

 dinal slice from each side of the kernel (Fig. 15.1 /, A) . Also prepare 

 some kernels for transverse sectioning by removing the basal and 

 stylar portions of the kernel, saving onh' the portion from the tip 

 of the coleoptile to the tip of the radicle. After the embryo is 25 

 days old, better infiltration of pieces for transverse sections can be 

 obtained by transversely bisecting the embryo at the scutellar node, 

 as well as removing the basal and stylar regions as above. 



The essential morphological structures of the kernel are well de- 

 veloped in 25 to 30 days, and the pericarp becomes hard and brittle 

 in 30 to 40 days. It is usually unnecessary to section the entire 

 caryopsis after these dates. The embryo can be extracted easily be- 

 tween the 15th and 40th day, or until the kernel becomes so hard 

 that the embryo is fractured if an attempt is made to dissect it out. 



After the kernel has undergone maximum natural drying, or even 

 if the kernel has been artificially dried for storage, the embryo can 





•A 



) 



w 



Fig. 15.7— a, Embryo of Lilium regale; b, embryo of Lotus corniculatus (courtesy of 

 Dr. Harold \\\ Hansen) ; c, embryo of Lycopersicum esciilentum. 



