15o Reproductive Structures of Vascular Plants 



The preparation of vegetative organs of the highly diverse mem- 

 bers of the phylum Tracheophyta, the vascular plants, is discussed 

 in a separate chapter because such organs require similar techniques 

 (Chap. 13). Similarly, the reproductive organs of the Tracheophyta 

 present common problems of processing and staining and are there- 

 fore brought together in the present chapter. Orders as well as Classes 

 ar used as major headings. 



Lycopodiales 



Ihe organization of the strobilus of the club mosses should 

 certainly be studied by dissection, and there is no point in embedding 

 entire strobili. Ascertain the stage of sporogenesis in each cone by 

 dissecting out a sporangium and crushing out the contents. Mature 

 sporangia containing dry, hard, brittle spores should not be embedded 

 unless a cytological study is to be made. Subdivide the cone 

 transversely, and kill in FAA, medium chrome-acetic, or Craf III. 

 Sections should be stained in safranin-fast green or iron hematoxylin. 



The gametophytes of these plants are exceedingly rare, although 

 they are said to occur in abundance in localized areas. Gametophytes 

 may be purchased preserved in FAA. The soft thallus is easily 

 sectioned in paraffin and stained. 



Selaginellales 



There is very little justification for making sections of the strobili 

 of these plants because dissections under a binocular reveal so much 

 more of the orderly organization of the cone. Dissected and crushed 

 sporangia likewise present a three-dimensional picture that is lacking 

 in sections. The study of nuclear details of sporogenesis and the de- 

 velopment of gametophytes within the spores is a task for the experi- 

 enced investigator. 



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