380 ANGIOSPERMS LESS. 



sporophylls or stamens (sp. ph. 6 ), and one of female sporophylls or 

 carpels (sp. ph. 9 ). 



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 

 ( nig. spg) in which is a single megaspore (ing. sp}. 



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

 off a pollen-tube (/. t} 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 : 

 m.r, 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 (p. t] : nu, nu l , the two nuclei. 



D, diagrammatic vertical section of a megasporangium, showing the 

 double integument (f l ,f 2 ), nucellus (net), micropyle (m.py), and mega- 

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

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

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



A pollen-tube (p. t} is shown with its end in contact with the 

 synergidse. 



E, semi-diagrammatic section of the megaspore of a young seed, 

 showing an embryo (emb} in the polyplast stage with its suspensor 

 (spsr) : also numerous vacuoles (vac} and nuclei (mi). 



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

 (/), micropyle (mpy\ 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.) 



Above the sepals comes a whorl of leaves (per*--}, usually 

 of large size and bright colour, forming in fact the most 

 obvious part of the flower. These are \hzpetals and together 

 constitute the corolla. The calyx and corolla together are 

 conveniently called the perianth, because they inclose the 

 sporophylls or essential part of the flower. The presence of 

 a well-marked perianth is characteristic of the majority of 

 Angiosperms, and distinguishes them from Gymnosperms, in 

 which this part of the flower is quite rudimentary (see Fig, 

 87, A. and B, per). 



