THE SOUTHERN PLANTER. 



543 



It is a plant interesting to agriculturist, not 

 on account of any beneficial results, but 

 on account of the mischief it does. I 

 have also here a specimen of the Dodder 

 (Cuscuta), which has been so mischievous 

 occasionally also in Clover fields, particu- 

 larly in Norfolk. The plant has flowers 

 like the Convolvulus on a small scale; it 

 belong to the family of the Convolvulacea), 

 the same family to which belongs another 

 pest, the Bearbind. This plant forms per- 

 fect seeds like the seeds of the Convol- 

 vulus, and the flowers are, in all respects, 

 as complete as the flowers of that plant. 

 When the seeds fall to the ground they 

 germinate like ordinary seeds, they stretch 

 out along the ground in a little narrow 

 w^ire-like process, and if that does not 

 meet with a clover plant it dies ; but if it 

 finds the clover plant, it makes its way to 

 it, and the older part of the original root 

 soon withers away. The part of the stem 

 which is attached to the clover produces 

 little papillae or peg-like processes of a 

 delicate structure, which drive their way 

 into the tissue of the stalk of the clover. 

 The plant derives the whole of its nourish- 

 ment, after the first early epoch of its 

 growth, from the juices of the plant which 

 it infests ; the plants are entirely parasitic. 

 But the modifications of parasitism by 

 means of roots are noi exhausted by such 

 plants as broomrapes and dodders ; for we 

 have? others which are imperfectly para- 

 sitic, and which have in this kind of para- 

 sitism a distinct constitution. Of these 

 are the weeds often found in pastures, 

 called the Eye-bright, the Yellow-rattles, 

 and some others. I have before me a 

 specimen of a Thesium, a plant also be- 

 longing to this class, which is rather rare 

 in this country. The roots at first attach 

 themselves to other plants like the broom- 

 rapes. A careful examination shows liitle 

 suckers or disc-like processes upon the 

 roots; but when the plant obtains a cer- 

 tain degree of vigour it ceases to be para- 

 sitic, it ceases to depend upon the nurse, 

 throws up a stem, becomes covered with 

 green leaves, and provides for its own 

 sustenance. The Mistletoe is an example 

 of parasite where the root ceases to exist 

 at a very early stage of growth. When 

 it germinates it produces a rootlet like anv 

 other seed. It attaches itself to the 

 branches of the trees it infests by the vis- 

 cid gummy or mucilaginous matter sur- 



rounding the seed. If it falls upon an old 

 branch covered with a corky bark it will 

 germinate, but nothing more ; but if it falls 

 upon a young shoot covered merely by a 

 delicate thin rind and sticks there, when it 

 begins to germinate the lower part of the 

 stem spreads out to a kind of disc, and 

 from the centre. This the little rootlet 

 penetrates through the spongy parts be- 

 neath the bark, making its way to the 

 cambium, where the new growth of the 

 nurse-plant will take place, so that the 

 seedling is brought exactly to the same 

 condition as a bud when it is grafted on 

 the stock in the ordinary operations of 

 gardening ; an organic connection is set 

 up, the tissues become vitally connected, 

 and the plant becomes, as it were, a branch 

 of the nurse-plant, and no longer produces 

 any root structure. Still, though it has no 

 root, unlike the broomrapes to which I 

 have adverted, it does produce green 

 leaves ; even its stem becomes green ; and 

 it decomposes oxygen ; therefore, though 

 it does not absorb its own food, it per- 

 forms some part of the processes of vege- 

 tation, and takes a share in the elabora- 

 tion of the food. There are interesting 

 cases of peculiar constitution in plants, 

 manifesting themselves in peculiar vital 

 qualities, as they may be fairly called, in 

 the roots. It certainly must be regarded 

 as a vital peculiarity in these plants that 

 they attach themselves in this way not 

 merely to other plants, but to other par- 

 ticular parts and even to particular species 

 of plants. 



In preparing this lecture, I have noted 

 down in regard to this subject some facts 

 and conclusions as to the functions of roots 

 generally in reference to the supposed 

 phenomena of choice. The above are 

 illustrations of what may be called in 

 roots a choice of food, and they may be 

 taken as serving, in part, as evidence on 

 the general question. But we must not 

 regard this kind of choice in the same 

 way that we regard choice of food in 

 man, for example. The plant cannot go 

 and seek out what food it pleases, but it 

 has a kind of negative choice. It cannot 

 grow upon food that is unsuitable ; it must 

 have that food which is suiied for its par- 

 ticular constitution. If the food is indif- 

 ferent, the plant will not grow, but need 

 not be absolutely injured. If the food is 

 noxious, the plant will be killed by it, but 



