Reproductive Structures of Vascular Plants 169 



A detailed discussion of the morphology and tcchnicjiies applicable 

 to other orders of gymnosperms is given by johansen (1940) . 



Angiospermae 



The angiosperms are usually the central feature of the study of 

 reproduction in plants, representing the climax in the development 

 of reproductive organs. Floral types and features of floral organs are 

 studied best by dissection and whole mounts of fresh or preserved 

 material. 



THE FLOWER 



Microtome sections are indispensable for the study of vasculation 

 and histogenesis of floral organs. Each species is virtually a problem 

 in itself; therefore, this discussion will be limited to the methods used 

 for the successful preparation of a few useful subjects. Buds of lily 

 and tulip are among the most satisfactory subjects for entire flower 

 buds. The very young buds are large and easy to handle. Embedded 

 buds can be accurately oriented for sectioning, and the parts are so 

 large that elementary students can locate and recognize the parts on 

 the slide. Lily buds are available over a considerable period, 

 beginning ^vith Lilluiu utubellatum and L. elegans in May, to L. 

 tigrijiinii in August. ^Vell-de^ eloped floral parts are shown in buds 

 that are less than 5 mm. long (Fig. 15.4) . Cut off at the base of the 

 perianth, and remove successive slices from the tip until the tips of 

 the anthers have been cut off. Drop into the killing fluid and pump 

 vigorously. Fair fixation is obtained in FA A, but superior results are 

 obtainable with Allen-Bouin II. Sectioning and staining are delight- 

 fully easy. Begin sectioning at the base of the flower, discard the ribbon 

 until the sections include anthers and ovary, and discard the block 

 when ovules are no longer present in the apical portion of the ovary. 



Buds of tulip for entire sections of young flower buds are ob- 

 tained from bulbs during late fall. Many varieties of Darwin tulips 

 are in a suitable stage from mid-October to early November. Meiosis 

 was found to occur in several Darwin \'arieties in October. Kill in 

 Allen-Bouin II and carry through an alcohol-xylene, dioxan, or 

 butanol series for entire young flower buds; for an older ovary follow 

 the recommendations for the lily. Cut open the bulb, and dissect out 

 the complete flower bud. Trim and kill as with lily. 



Maithiola, the common garden stock or gillyflower, furnishes a 

 suitable dicotyledonous flower for complete sections. Remo\e indi- 



