1889.] DEPARTMENT OF BOTANY 



WEEDS 



Iii a previous report, Dr. Halsted, now of ^ 

 has culled your attention to several troublesome 

 ject of considerable importance to the farmer. I shiH^iftB^fcf'le^Cvhich 

 have come under my notice during the year. It will e%^amj*f1)e of great 

 interest to the farmers of Iowa to know that the troublesome European par- 

 asite. "Clover Dodder,'' has made its appearance in Missouri. 



A short time ago. I received from Mr. Henry Wallace, of the Homestead, 

 a specimen of what he thought might he Clover Dodder. The material was 

 carefully compared with specimens in the herbarium of the Agricultural 

 College, and the conclusion I reached was that it could be nothing else but 

 Clover Dodder (Cuscuta epithymum, L.) I republish apart of the Home- 

 sU '/'/ article, and some more additional facts concerning this pest, that farm- 

 ers may be on their guard. 



Mr. Downing's letter to the Homestead is as follows: 



"I send sample of a vine that is killing clover, not on my farm alone, but 

 it lias quite a start in this section, and all from seed shipped here last spring. 

 J send you some that has dried up, and some green. As soon as it kills the 

 clover (or anything else that it gets hold of) it dies and leaves the ground 

 bare; but the ends of the vine keep on spreading among anything green. 

 There are spots now already dead that are two or three rods across. I hope 

 you will give information as to what it is, also how to get rid of it." 



Mr. Downing's plant is without doubt Clover Dodder (Cuscuta Trifolii 

 Bab, or, as it is now called, C. epithymum, L). The dodders belong to the 

 Morning-glory family (Convolculaceae), to which the common wild Morning- 

 glory, or Bindweed Sweet potato belong. This order contains a good many 

 plants which are troublesome weeds in many parts of the world. 



The genus Cuscuta or Dodder contains a good many species, upwards of a 

 hundred having been described by botanists. Of these, forty-four are found 

 in America, twenty-nine of which are indigenous to the United States. 

 Among these American dodders one is frequently found on the high bush 

 blackberry (rubus vUlosus). The others are found on various native plants. 

 such as smart weeds, willows, hazels, on various composites, like golden-rod, 

 sunflowers, etc. 



The dodders are leafless (excepting the small scales on the stem) herbs of 

 reddish or yellowish color, with thread-like stems twining around the plants 

 upon which they live. They pierce the bark with their small and short root- 

 let-, which are called suckers, or haustoria. The seeds are small; yet there 

 is stored sufficient nourishment in them to give the growing plants a good 

 start. Germination takes place in the soil, the young plantlet grows suffi- 

 cient in length to allow it to come in contact with the plant upon which it 

 lives, when it immediately sends in it> suckers and thus becomes established 

 upon the plant as though it were a part of it. It is usually stated that dod- 

 ontain no chlorophyll, but recent investigations show that they contain 

 ut least a small amount, but probably not enough to enable them to make 

 very much starch out of crude material. Ordinary green leaves contain a 

 great deal of this chlorophyll, or green coloring matter, and. hence, are able 

 to prepare their own food. Plants like dodders, which derive their nourish- 

 ment from the host uj^on which they live, are said to be parasitic. 



