372 



SELAGINELLA 



LESS. 



corresponding male structure, purely endogenous. A few 

 ovaries (ovy) are formed on it, each consisting of a short 

 neck, an ovum, and two canal-cells afterwards converted into 



spar 

 spsr 



FIG. 86. Reproduction and Development of Selaginella. 



A, diagrammatic vertical section of a cone, consisting of an axis bear- 

 ing close-set sporophylls (sp. ph}, on the bases of which microsporangia 

 (mi. spg} and megasporangia (mg. spg) are borne. 



B, section of a microspore, showing the outer coat (mi. sp}, prothallial 

 cell (prt)i) y and multicellular spermary (spy). 



C, vertical section of a megaspore, the wall of which (mg. sp} has been 

 burst by the growth of the prothallus (prtfi) : its cavity (prth'} contains 

 a large-celled tissue, the secondary prothallus : in the prothallus are 

 three ovaries (ovy}, that to the left containing an ovum, that to the right 

 an embryo (emb} in the polyplast stage, and that in the centre an embryo 

 in the phyllula stage, showing stem-rudiment (st}> foot (/), and two 

 cotyledons (ct} : both embryos are provided with suspensors (dotted) 

 (spsr), and have sunk into the secondary prothallus. 



(Altered from Sachs. ) 



mucilage : there is no venter, and the neck consists of only 

 two tiers of cells. 



The oosperm divides by a plane at right angles to the 

 neck of the ovary, forming the earliest or two-celled stage of 



