xix.'] CLOVER DODDER. 121 



For the same period the dodder threads, as a rule, have 

 produced no suckers, although in one or two erratic ex- 

 amples we have seen suckers whilst the embryo thread 

 was still within the burst testa. Dodders bear minute 

 transparent scales on their threads as equivalents to 

 leaves, but we have not seen them in clover dodder till 

 the young plants have been several weeks old. When 

 dodder twines round a young seedling clover, the rapidly- 

 growing clover carries the dodder away from the ground, 

 the old withered testa being sometimes still attached to the 

 dodder thread for a week or two. A dodder plant a few 

 weeks old, on a young clover leaf, is shown enlarged ten 

 diameters in Fig. 52. As the clover grows the dodder 

 now grows with it, and the parasite is lifted higher and 

 higher from the ground. As the spring and summer 

 advance, the dodder flowers profusely, and as the clover 

 plants grow in size and come in contact with each other, the 

 dodder spreads from one host to another. The dodder, in 

 growing, repeatedly branches and rebranches, and throws 

 out long arms, so that during a single summer one or 

 two infested clover plants will help to spread the dodder 

 over a large area. The parasite cannot live on the remains 

 of the plants it has destroyed, so, in the process of growth, 

 it leaves the central clover plant for other plants at the 

 circumference of a dead circle of clover, which may be 

 many feet or even yards in diameter. 



At Fig. 53 is shown a fragment of clover stem cut 

 from the top of the stem at E, as illustrated at Fig. 

 47. This illustration is enlarged fifteen diameters to 

 show the connection by suckers of the twining dodder 

 with the stem of the clover. On examination with the 

 microscope it is seen that not only has the dodder no 

 roots or true leaves, but it is destitute of green colouring 

 matter, the substance which helps to elaborate the food 

 of plants, and which occurs so abundantly in clover. 

 Dodder has none of the small mouths or organs of tran- 

 spiration so frequently adverted to in these notes, but its 



