322 Peirce. —On the Structure of the Hailstorm 
distinguish the different elements composing the phloem of 
the bundles ; yet in a thin section, stained with an aqueous 
solution of aniline-blue, the presence of callus-plates in the 
narrow sieve-tubes is made evident (see Fig. VII, Plate XV, 
red lines represent callus-plates). The sieve-tubes of these 
bundles unite directly with the sieve-tubes in the adjacent 
bundles of the host, as is shown in Fig. VIII (the brown 
shading represents cells of the host, the red of the parasite). 
A conducting system is thus installed such as we have already 
found in the haustoria of the Cuscutas. A study of the 
further development of the buds is beyond the scope of the 
present paper. 
Owing to the lack of germinating seeds it is impossible 
absolutely to determine the morphology of what has been so 
far described ; but, from analogy with Viscum album for 
example, we may infer that the seed, germinating on the 
surface of the host-plant, sends a primary root into its tissues, 
and that this root soon branches. This root and its first 
branches may be composed of differentiated tissues. In 
Viscum , as shown above, the branches grow in the cortex 
near the surface of the host. In Brugmansia , the primary 
root of the seedling probably does not branch so near the 
surface, but rather in the cambium of its host. Such at least 
seems to be the case in Pilostyles Hausknechtii , Boiss., as 
described by Graf Solms h These branches, making their 
way through the cambium, have no need of conducting 
tissues, their cells being individually nourished, like those of 
the cambium, from the adjacent tissues. They are therefore 
composed only of thin-walled parenchymatous cells. In the 
root of Cissus we recognize the branches as the chains of cells 
already described. By the rapid multiplication of their cells 
at certain points buds are formed, beginning as small masses 
of parenchyma, which later increase in size, and in which 
fibro-vascular tissues are differentiated. The chains of cells 
growing in the cambium have, as their sole function, to 
nourish themselves, a very easy matter owing to their position. 
1 Ueber den Thallus von Pilostyles Hausknechtii. Botanische Zeitung, 1874. 
