MORPHOLOGY OF HIGHER PLANTS. 



379 



bodies which are borne on the placentas, and which, after f ertihza- 

 tion, develop into seeds. The number of ovules varies considerably 

 — there may be but one, as in the almond, or there may be a large 

 number, as in the watermelon. 



There are several principal forms of ovules (Fig. 220) recog- 

 nized, of which the following may be mentioned: (i) atropous, 

 in which the ovule is straight and erect on its stalk, as in the 

 Urticaceae ; (2) anatropous, in which the ovule is bent over on to 

 the stalk so as to be in an inverted position, the line of attachment 

 of the ovule and stalk being known as the raphe (Fig. 230, n) ; (3) 

 CAMPYLOTROPOUS, in which the ovule is bent upon itself, as in 

 Stramonium, this form being less frequent than the other two. 

 Most of the ovules of flowering plants are anatropous. 



Fig. 220. Three positions of ovules. A, atropous; B, anatropous; C, campylotropous. 



(f) funiculus or stalk; (c) chalaza, or point of union of nucellus and integuments; (k) nucellus 

 or megasporangium; (em) embryo-sac or megaspore; (ai) outer integument; (ii) inner 

 integument; (m) foramen or orifice for entrance of pollen tube, known as the micropyle 

 in the seed; (r) raphe. — After Prantl. 



Stamen. — As already indicated, the stamen consists of a 

 stalk-like portion called the filament, and a specialized portion 

 which bears the sporangia, called the anther (Fig. 78). The 

 filament may be long or short or wanting. It is commonly thread- 

 like, but varies considerably, and is sometimes leaf-like. 



The Anther is the essential part of the stamen (Fig. 221) 

 and consists of two lobes, each of wdiich is composed of two divi- 

 sions or pollen sacs (Fig. 79). These sacs contain the pollen, 

 which is commonly discharged either through a longitudinal suture 

 or line of dehiscence, or through an opening at the tip. The 

 anthers may be variously attached to the filament (Fig. 221). 

 When they face the axis of the flower they are said to be introrse, 

 as in the Violaceae, and when they face the perianth they are said 



