442 



FERTILIZATION AND FORMATION OF FRUIT IN PHANEROGAMS. 



vigorous embryo, and in providing it with adequate safeguards against unfavour- 

 able external conditions, and with means of dispersal, when the time comes for the 

 seed to be detached from the parent plant and to take up an independent existence. 



Whilst still attached to the parent plant, the embryo needs protection against 

 the ravages of animals, and against unfavourable climatic conditions. Means of 

 protection against the former are provided sometimes on the seed-coat, in other 

 cases on the wall of the ovary; or they may be on other structures associated with 

 the flower, or upon the flowering axis itself. These defensive arrangements fall 

 into several groups. First of all, there are thorns, prickles, and spinous bristles, met 



Fig. 336. Fruits and Seeds of Conifer*. 



1 Branch of Yew (Taxus baccata) with ripe seeds, each inclosed in its aril. 2 Tip of ovule of same projecting from betweei> 

 the scales of the little fertile shoot. 8 Longitudinal section of the same. * Young seed of the same only partly inclosed 

 in its aril. 6 Longitudinal section of the ripe seed of the same, showing the aril. 6 Branch of the Arbor Vitse (Thuja 

 orientalis) showing female flowers and ripe, burst cones. 7 Branch of Juniper (Juniperus communis) showing berry-like- 

 cones. 8 Longitudinal section of one of these cones. Female flower of Juniper. 1, 6 , and * nat. size; the other figs, enlarged. 



with especially on the ovary and immediate envelopes of the fruit. The capsule of 

 the Thorn-apple (Datura Stramonium), that of the Anatto (Bixa Orellana, see fig. 

 338), the long 3-valved fruits of Schrankia (see fig. 339 2 ), the pods of the Russian 

 Liquorice Plant (Glycyrrhiza echinata), the persistent calyx of a steppe -plant,. 

 Arnebia cornuta, and the cupule of the Chestnut (Castanea vulgaris, see fig. 339 4 > 

 may serve as examples. Several Pines, of which the North American Pinus- 

 serotina is a type, have cones the scales of which are produced into sharp spines 

 (see fig. 337 2 ), so that the seeds are inaccessible to animals till such time as 

 the scales separate and the winged seeds are committed to the wind. Of interest 

 in this connection are certain Crucifers (Tetractium quadricorne, Matthiola 

 bicomis, M. tricuspidata, fig. 339 3 ) in which, at the end of the fruit just below the- 

 scar of the style, 2, 3, or 4 stiff spines are formed, which make these fruits unaccept- 



