LESS, xxxiv MORPHOLOGY OF FLOWER 471 



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 

 off a pollen-tube (p.t) through the tissue of the style to the micropyle of 

 the megasporangium. 



B 1 , diagram of a female sporophyll from the dorsal 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 ; the larger is the vegetative-cell. 



C 2 , the same, sending out a pollen-tube (/. t); nu, nu l , the two nuclei : 

 the generative nucleus has not yet divided. 



D, diagrammatic vertical section of a megasporangium, showing the 

 double integument (f^,/'*), nucellus (#<r/), micropyle (m.py), 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- 

 gidse (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 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 (m. fly), 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. ) 



of the nodes, so that all the leaves sepals, petals, 

 stamens, and carpels arise close together from a small 

 area. Thus, the angiospermous flower, like the gymno- 

 spermous cone, is a modified shoot of limited growth, 

 having its axis shortened to a floral receptacle and its 

 leaves modified to form the various floral organs. The 

 composition of the flower may therefore be expressed in a 

 diagrammatic form as follows : 



f p ,, /Protective Sepals (Calyx). 



Floral Receptacle \_, f ) \Attractive Petals (Corolla). 



= Axis of Shoot / es | Sporo- J Male Stamens (Andrcecium). 



^ phylls (Female Carpels (Gyncecium). 



