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8. The embryo is coiled in the seed and imbedded in the food 
substance. Examine the photographs of plates taken from Koch’s work. 
DRAW. 
9. If available, examine the dodder seedlings and note how 
they first attack the host-plant. Examine N. Y. (Geneva) Bul. 305, 
pl. 38, and Koch’s pl. 1, fig. 1-3. Make prawincs to show the characters 
of the seedling and its method of attacking the host. 
As soon as the seedling has attached itself to the host, the vestigial 
root by which it was anchored in the soil, shrivels and dies. The twining 
stem, however, feeds on the host, grows rapidly and by branching 
spreads to neighboring hosts. Study the dodder plant on the host pro- 
vided. OBSERVE :— 
10. The type of branching; opposite or alternate? 
11. The leaves; their location, size, shape, color and abundance. 
How are these foliage conditions to be accounted for? 
Untwine and separate a portion of the dodder thread from the host- 
stem. OBSERVE :— 
12. That it is attached at some points. At such places the spirals 
are shorter and are tight about the stem. 
13. With the hand-lens, the rows of minute punctures in the 
host-stem where the dodder was attached; the oval depression about each. 
14. With the hand-lens, the corresponding row of concave 
sucker-like disks on the dodder stem,—the attachment-disk; the minute 
elevation at the center of each disk,—the broken-off haustorium. 
15. The aborted haustoria in places along the dodder stem 
where it failed to come in contact with the host. 
Make a prRawine of a portion of a host-stem with entwined dodder 
to show all the points brought out in 10-15. 
Cut thin cross-sections through the clover and dodder stems at the point 
where haustoria are attached. Cover and examine under the low-power. 
OBSERVE -— 
16. In the clover stem, the large pith, the vascular cylinder, 
the cortex, and the epidermal layers. In the vascular cylinder, note the 
xylem containing the large ducts, and the phloem which. consists of soft 
sclerenchyma within and the lighter area of sclerenchyma-fibers without. 
17. In the dodder stem, the haustorium. Note the shape of 
the attachment-disk in cross-section; its relation to the haustorium; 
where the haustorium arises and how it penetrates the host. Note what 
happens where it comes in contact with the sclerenchyma-fibers. Toward 
which tissue of the host-stem does it grow? Why? Note the spiral 
ducts in the center of the haustorium. 
Make diagrammatic DRAWINGS of the host-stem and the dodder stem 
to show the relative sizes and relation of parts. 
With the low-power, examine the stained longitudinal sections of the 
haustorium of dodder on Impatiens (touch-me-not). NoTE:— 
18. The long thread-like cells extending out from the tip and 
sides of the haustorium into the cortex, pith, and sometimes into a bundle, 
making a connection with a conductive vessel of the host. 
19. The layer of crushed cells at the point where the haustorium 
emerges from the dodder stem. Does the epidermis of the dodder con- 
tinue about the haustorium? What becomes of it? Are the cells of the 
host crushed? What is the function of the thread-like cells? 
