446 



FERTILIZATION AND FORMATION OF FRUIT IN PHANEROGAMS. 



branches keep browsing animals away, whilst those inserted lower down which - 



d earthwards, prevent mice from climbing up the plant 



A peculiar protective contrivance has been observed on the calyx of several 



Labiates ^. Thymus, Cala^tha, Ballota. The corolla falls away after fertilize 



but the calyx persists, forming a sheathing envelope for the 4 nutlets. For the 



better protection of these nutlets the mouth of this cup-like envelope is closed by 



IntaT Trt, ' Tf ^ WhiCh i8 im P enetrable to small, seed-devouring 

 animals. A further use of these envelopes in seed-dispersal will be alluded to in 

 another place. 



In other cases fruits are protected against unwelcome guests, not by spin, 

 structures but by the elongation of their stalks during ripening, rendering hem 

 e T1 " 



F K > ~ 



V .syl^ca). Should by any chance a pod be accessible to these animals, by some 



other route, it is as good as lost, as the nutritious seeds of these plants are much 

 sought after by them. Cherries also, on their long stalks, no doubt derive consider 

 able immunity from earwigs, centipedes, &c., as those which fall to the ground 

 are speedily attacked and devoured. 



In the case of seeds whose dispersal depends on the attraction of animals by 

 sweet, fleshy ^pericarps these tissues are the reverse of appetizing before they are 

 ripe; not until the seeds are ready to be separated from the parent plant do fruits 



Cher P, be ~ ttra f Ve - " *ly necessary to cite as instances unripe 



Ohemes, Plums Apples, and Grapes. It was stated on a previous occasion (vol. i 



2), when dealing with chemical changes occurring in plant-tissues, that the 



shy parts of frmts are rendered disagreeable to animals before they are ripe by 



the presence of bitter or poisonous glucosides, &c. Later on these substances are 



altered, perhaps under the influence of the acids, which are present in large quanti- 



ty unripe frmts, and their place taken by sugars and other harmless laterials; 



ntt ! t /7 I Uaattractive ' and e P"M^ becomes, on ripening, a 

 atnt ous food, much sought after by animals, which, at the same time, un^on- 

 nously Asperse the contained seeds. In this connection the Walnut (Juglans 

 7 mStrUCt UntU n the * <h- really the 



, not known at this stage that the "nuts" are ever interfered 

 ith by nutcrackers or other animals. But on the ripening of the seed the fleshy 

 envelope splits, and the "nut" becomes accessible 



.ther cases it is not by acids or bitter stuffs that the seeds are protected, but 

 by strong-seen ed resinous or sticky substances, which are contained in the cells 



fuit - Thus> in the scaies f the f 



cut wth a k I reSm ^ PreS6nt Until the S6eds are rf P e - If the - be 



h u ost dTffic ^ " w ""^ ^ "" ^ ^ rem Ved fr m the Uade - ith 

 t difficulty. Were a nut-cracker to peck the scales at this stage to 



obtain the young seeds, its beak would get all besmirched with the resin t 



