LESS. XXXIV MORPHOLOGY OF FLOWER 471 



The male sporophyll bears microsporangia (nii. 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^ diagram of a female sporophyll from the dorsal aspect, and B^ 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*, a microspore, showing the two cells (a and b) into which its 

 contents divide ; the larger is the vegetative-cell. 



c^ the same, sending out a pollen-tube (p. t); nu, tiu^, the two nuclei : 

 the generative nucleus has not yet divided. 



D, diagrammatic vertical section of a megasporangium, showing the 

 double integument (/^/*), nucellus («<•/), micropyle {m.py), and mega- 

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

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

 gidee {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 m^aspore 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 

 (/), micropyle (w. py), perisperm (per) derived from the tissue of the 

 nucellus, and endosperm {ettd) formed in the megaspore and containing 

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

 and root {r). 



(b^, after Behrens ; c*, c'', 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 : — 



TpAri^ntV. /Protective— Sepals (Calyx). 

 Floral Receptacle "i^ J reriamn ^Attractive— Petals (Corolla). 



= Axisof Shoot / j Sporo- /Male — Stamens (Androeciura). 



^ phylls \Female — Carpels (Gynoecium). 



