24- 



PLANT LIFE. 



is divided into as many chambers as there are component 

 carpels, and the partition by which the chambers are sepa- 

 rated represents the adjacent parts of the two carpels. Or 

 the carpels may unite with each other at their edges only, so 

 -rr'sr-^^Tj^s, that the line of union is at the outside 

 ^^ s— cg^l ^^^ of the pistil. In this case the ovulary 

 will have a single chamber. In both these 



FlG. 252. — A transverse . 



section of the capsule of methods of union the normal number of 



shepherd's purse. The , 



pistil consists ,,f two chambers in the ovulary may be increased 



carpels, at whose united 



edges two placenta: are by OlltglOWths from the Carpels them- 



formed carrying the 



ovules (now seeds). The selves, as in figure 252, where Jrom the 



partition from one pla- 

 centa to the other is an united edges of the carpels a plate of tis- 



outgrowth (false parti- 

 tion) and not part of the sue has grown out to meet a correspond- 



carpel. Magnified about 



6 diam.— After Bessey. ing one from the other side, so that what 

 should be a one-chambered pistil has become two-chambered. 

 (Compare also fig. 276.) Even simple pistils are subject to 

 such subdivision of their interior (fig. 253). 



Fig. 253. Fig. 254. 



Fig. 253. — Lower half of the pistil of Astragalus canadensis. It consists oi only one 

 carpel, but is divided into two chambers by a false partition, an outgrowth from the 

 midrib of the leaf. Magnified several diam — Alter dray. 



Fig. 254— Two stages in the development of the ovule of the currant, ./.a median 

 longitudinal section ol a young ovule; n, the sporangium; //.inner integument be- 

 ginning to develop as .1 nng at base oi n ; .'/, the fundament of the outer integument ; 

 »r, the mother cell of the niegaspores ; /,', a similar section of tin sporangium alone, 

 older, showing »/', ;//", «/'", the daughter cells of m ; ///'". only becomes a perfect 

 spore; m' and m 1 ' do not develop further and become destroyed. Contents of cells 

 not shown. Magnified 350 diam. — After Warming. 



340. Ovules. — An ovule consists of a megasporangium 

 partially enveloped by one or two outgrowths from beneath. 



