^34 



HINTS AND NOTJ'.S 



Id Ih' a tondi'iicy tor llu- plants to stiii,tj)^li- 

 iDwaids pcic-niiial lial>il,s. 



Relative Absence of Insects. lCin|jliasis has 

 been laid upon tlii' close ranks of the corn 

 itself and llu- slrui;fglf of the plants towards 

 the lii;hl. The cornlield is indeed extremely 

 inaccessible tor all classes of animal life; 

 attention should be drawn to this aspect, and 

 lists of animals noticed drawn up. 



It is true that one may lind a j^dod many 

 insects and other small animals in a cornlield 

 especially associated with the jjround tlora, 

 where beetles, spiders, and myriapods are not 

 uncommon. Often one may see liulhillies 

 soaring; over the cornfield, but lew of Ihem 

 settle, and the food plants of llieir lar\.e .are 

 not usu.illy cornlield species. 



The niijht-tlowerinj^ Catch-tly a[ul the While 

 Campion are exceptions to this rule that plants 

 depending on Lepidoptera are absent from the 

 cornfield. Cross-pollination by insect ajfency 

 is on the whole rare. 



Difficulties of Natural Seed Dispersal. — The 

 groups of plants found in cornfields are as a 

 whole deficient in adaptation for seed dispersal 

 by animal agency; for except the Field Bu- 

 gloss, Corn Buttercup, and Wild Oat, there are 

 none which are liUely to catch in the wool or 

 fur of animals. 



Only a few have special devices of their own 

 apart from the external agency of the wind 

 for dispersal to a distance, such as Shepherd's 

 Needle and Heart's Ease. The seeds of (iold 

 of Pleasure and Corn Gromwell may be eaten 

 by birds. 



A large number are dehiscent, dry fruits, 

 which split open when ripe, as Charlock and 

 Larkspur, and the Scarlet Pimpernel has a 

 special type, or pyxis, with a lid which opens 

 when the seeds are ripe. The bulk of the 

 plants have fruits of the pepper-box type, as 

 the Poppy, or censer fruits, which scatter their 

 numerous small seeds, when the wind jerks 

 the flowering stems, around the plant itself. 

 In a high gale they may be driven some dis- 

 tance. .A tew, as Corn Sow Thistle, have a 

 feathery papjuis which assists in their dispersal 

 by the wind. 



The closeness of the cornstalks, by its shield- 

 ing effect, rather counteracts the action of the 

 wind. And the seeds of the majority of the 

 plants are thus as a rule .scattered over a small 

 area. Hence the patches of the same plant in 

 a cornfield in addition to the even dispersal of 

 most as a result of harrowing, &c. 



Man's Agency. — In a cornfield one is met 

 at every turn by artificial agencies. Not least 

 is the direct intervention of man causing the 

 distribution of cornfield weeds. The cultural 

 operations themselves are so far-reaching that 



there is very little scope for any other 

 natural agency in the matter, except that of 

 the wind, which may not only disperse the 

 seeds in one cornfield over the whole area, 

 but also cause dispersal from one area to an- 

 other. 



The operations of preparing the ground Inr 

 corn are not in themselves selective so far as 

 the dominance or otherwise of the plants as- 

 sociated with corn are concerned, though 

 indirectly they are so, as has been shown. 

 But there is a direct influence upon the weed 

 tlor.i when weeding is undertaken, as in clean 

 fields it always is. In this case the farmer or 

 his men exercise a good deal of personal dis- 

 crimination as to what plants are to be specially 

 eradicated and what may with advantage be 

 left. Thistles are of course exterminated 

 where possible, and so are such Grasses 

 as Couch Grass. The Corn Buttercup and 

 Charlock also are regarded as special enemies 

 of the farmer, and in some areas the Corn 

 Marigold has been laid under the ban, and 

 a royalty paid upon its eradication. .Such 

 poisonous plants as Fool's Parsley and Darnel 

 are harmful for wheat-growing purposes, and 

 are also exterminated wherever they occur. 

 Hence the character of the cornfield flora must 

 be regarded as largely dependent upon man 

 himself. 



Easier Struggle for Existence. — There are 

 two distinct features of the cornfield that are 

 compensative in effect in relation to each other. 

 The struggle of the cornfield weeds amongst 

 the corn towards the light has already been 

 emphasized, and this may be said to mould 

 their characters more than any other factor. 

 The difiiculties that cornfield plants have to 

 contend with in this connection are very great ; 

 and they would be even more so if the plants 

 were perennial, and under necessity of storing 

 up reserves to help them over the resting 

 season and to make a fresh start in spring. 

 But this duty is not required of them. Hence 

 the light requirements are not so vital as 

 might seem to be the case. 



If this were so, however, the plants have not 

 to struggle for their existence against over- 

 crowding or lack of nutritive elements derived 

 from the soil, for the latter is open and not 

 thickly colonized, so that the intensity of the 

 struggle for the light is directly counteracted 

 by the favourable conditions in the soil. This 

 is shown bv the luxuriance of such plants as 

 Red or White Dead Nettle growing in a turnip 

 field, compared with their growth in a corn- 

 field, and Selfheal is a good example of the 

 same kind of thing. W'all Speedwell, which 

 sometimes grows in a cornfield, is much more 

 luxuriant than when growing on a wall, and 



