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| Patterns of Embryo Development |
| Following Syngamy, the Zygote divides transversely to produce an upper (Epi) and lower (Hypo) cell. These are called Epibasal & Hypobasal respectively. |
| One of these will produce the Embryo
Proper & the other will produce the absorptive Foot. |
| Exoscopic development occurs when the Epibasal Cell -> Embryo Proper |
| Endoscopic development occurs when the Hypobasal Cell -> Embryo Proper |
| The Embryo grows into the Gametophyte when
Endoscopic development occurs. Thus, it can gain protection from the environment & nourishment from the Gametophyte. This makes its survival more probable and is considered to be an important positive adaptation. |
| Embryo Development in Psilotum is Exoscopic! The Epibasal Cell -> the Embryo & the Hypobasal Cell -> Foot |
