148 Boeshorc — The Morphological Continuity of 



and Christisonia. The extent of the root system of Lathraea 

 is very limited; the roots are semi-woody semi-fibrous. This 

 genus, as already pointed out, is by some authors regarded as a 

 member of the Scrophulariaceae, by others as a member of the 

 Orobanchaceae. It offers a graded transition from pale green 

 and greenish purple to purple red genera like Buchnera, Har- 

 veya and Hyobanche of the Scrophulariaceae to Orobanche 

 of the Orobanchaceae. Kerner (15, p. 182) has described the 

 parasitism of Lathraea. He says: "The young root of the seed- 

 ling grows at first at the expense of reserve material stored in the 

 seed, penetrates vertically into the earth and sends out lateral 

 branches, which, like the main root, follow a serpentine course 

 and search in the loose damp earth for a suitable nutrient sub- 

 stratum. If one of these meets with a living root belonging to 

 an ash, poplar, hornbeam, hazel, or other angiospermous tree, 

 it fastens on to it at once and develops suckers at the points of 

 contact; these suckers are at first shaped like spherical buttons, 

 but soon acquire, as their size increases, the form of discs adher- 

 ent to the host's root by the flattened side and with the convex 

 hemispherical side turned toward the rootlet of the parasite. 

 These discoid suckers cling to the root attacked by means of a 

 viscid substance produced by the outermost layer of cells. As 

 in the case of the parasites already described, a bundle of ab- 

 sorption-cells grows out of the core of each sucker into the root 

 of the plant serving as the host, and the tips of the absorbent 



cells reach to the wood of the root" "The 



roots, which issued originally from the seedling, and their suckers 

 have long since ceased to meet the requirements in respect to 

 nourishment of so greatly augmented a structure, and therefore 

 additional adventitious roots are produced every year, spring- 

 ing from the stem and growing towards living woody branches 

 of the thickness of a finger, belonging to the root of the tree or 

 shrub that serves as host. When there, they bifurcate, forming 

 numerous thickish filiform arms, which lay themselves upon the 

 bark of the nutrient root and weave a regular web over it. 

 Sometimes two or three of these root filaments of the parasite 

 coalesce, forming tendrils, and the resemblance to a lace-work 

 or braid is then all the more pronounced. Suckers, such as 

 have been described, are developed by these root-filaments 

 laterally, and more especially on the ends of the branches." 



