376 ANGIOSPERMS 



sporophylls or stamens (sp. ph. <$ ), and one of female sporophylls or 

 carpels (sp. ph. ? ). 



The male sporophyll bears microsporangia (mi. spg) containing 

 microspores (mi. sp). 



The female sporophyll consists of a solid style (st) terminated by a 

 stigma (stg), and of a hollow venter (v) containing a megasporangium 

 (mg. spg] in which is a single megaspore (mg. sp). 



On the right side a microspore is shown on the stigma, and has sent 

 ofif a pollen-tube (/. /) through the tissue of the style to the micropyle 

 of the megasporangium. 



B 1 , diagram of a female sporophyll from the distal aspect, and B 2 , the 

 same in transverse section, showing the folding in of its edges to form 

 the cavity or venter in which the megasporangia (mg. spg) are enclosed : 

 mr, the midrib. 



c 1 , a microspore, showing the two cells (a and b) into which its 

 contents divide. 



c' 2 , the same sending out a pollen-tube (/. t) : nu 1 , nu 1 , the two 

 nuclei. 



D, diagrammatic vertical section of a megasporangium, showing the 

 double integument (t l , f 2 ), nucellus (ncl), micropyle (mpy), and mega- 

 spore (mg. sp) : the latter contains the secondary nucleus (nu) in the 

 centre, three antipodal cells (ant) at the proximal end, and two syner- 

 gidae (sng) and an ovum (ov) at the distal end. 



A pollen tube (/. /) is shown with its end in contact with the 

 synergidae. 



E, semi-diagrammatic section of the megaspore (mg. sp) of a young 

 seed, showing an embryo (emb) in the polyplast stage with its suspensor 

 (spsr) ; also numerous vacuoles (vac) and nuclei (nu). 



F, diagrammatic vertical section of a ripe seed, showing the seed-coat 

 (t), micropyle (inpy), perisperm (per) derived from the tissue of the 

 nucellus, and endosperm '(end) formed in the megaspore and containing 

 an embryo in the phyllula stage with stem-rudiment (st), cotyledons (ct), 

 and root (r). 



(B 1 after Behrens ; c 1 , C 2 , and E altered from Howes.) 



abbreviated shoot, consisting of a short axis (fl. r) of limited 

 growth bearing four whorls of leaves, of which those of the 

 two distal whorls are sporophylls. 



The axis of the floral shoot (A, fl.r is usually broad and 

 more or less conical in form and is called the floral receptacle. 

 The leaves of the lower or proximal whorl (per 1 ), usually 

 from three to five in number, are small green bodies which 

 cover the other parts in the unopened flower : they are called 

 sepals and together constitute the calyx. 



