LIFE HISTORY OF AN ANGIOSPERM 59 



2. In the Gymnosperms the sporophylls are usually inserted 

 either spirally or in whorls around a distinctly elongated axis, 

 whereas in Angiosperms the sprophylls are condensed to short 

 whorls or spirals set around a shortened axis, the floral axis or recep- 

 tacle, torus or thalamus, or, as in the more modified Angiosperms, 

 the floral axis may even become hollow. 



3. In Gymnosperms the microsporophylls or stamens are usually 

 sessile, whereas in Angiosperms the microsporophylls are nearly 

 always stalked. Rarely do we find sessile anthers among Angio- 

 sperms, an instance of this being seen in Mistletoe (Viscum) where 

 the anthers are set on the staminal leaf. 



4. In Gymnosperms there is a traceable prothallus or gametophyte 

 plant that later becomes the so-called "endosperm" of the gymno- 

 sperm, whereas in Angiosperms no recognizable prothallus has been 

 proven to exist. 



5. The stored food tissue in Gymnosperm seeds is prothallial tis- 

 sue loaded with starch, etc., whereas in Angiosperm seeds the stored 

 food tissue (endosperm) is a special formation after fertilization. 



6. Gymnosperms bear naked ovules and seeds while Angiosperms 

 bear covered ones. 



7. In Gymnosperms there are distinct recognizable archegonia 

 formed on or imbedded in the prothallus, whereas in Angiosperms 

 there are no distinct archegonia, only an isolated egg or eggs. 



8. In Gymnosperms there are not infrequently found several 

 embryos from one fertilized egg. This condition is called poly- 

 embryony. Polyembryony is unknown in Angiosperms, only a false 

 polyembryony being noticed. 



9. In Gymnosperms the secondary xylem (wood) tissue of roots, 

 stems and leaves consists either of punctated or scalariform cells, 

 whereas in Angiosperms the secondary wood tissue may be varied 

 in structural aspect. 



