PLANT ORGANS AND ORGANISMS' 
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cerifera , M. Caroliniensis, M. Gale , M. Macfarlanei, and Comptonia 
asplenifolia. The inciting organism has been isolated by him in 
pure culture according to Koch’s postulates and named Actinomyces 
Myricarum Youngken. 
The tubercles occur either singly, as is frequently the case on 
subterranean branches, in small groups the size of a pea, or in larger 
coralloid loose or compact clusters which frequently attain the size 
of a black walnut. Each tubercle is a short cylindrical blunt-ended 
root-like structure which branches di- or trichotomously after attain¬ 
ing a certain length. The branches frequently rebranch at their tips 
which grow out into long thread-like structures from 1-3 cm. in 
length that may also branch and become entwined about the roots of 
other plants. The color of the youngest tubercles is a pinkish-gray 
brown. As the tubercles become older their color changes to brown, 
dark-brown and even black. (For a detailed description of the 
Myrica and Comptonia tubercles and their inciting organism, con¬ 
sult, “The Comparative Morphology, Taxonomy and Distribution 
of the Myricaceae of the Eastern United States” by Youngken, in 
Contributions from the Botanical Laboratory of the University of 
Pennsylvania, vol. iv, no. 2, 1919.) 
THE BUD 
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Buds are short young shoots with or without rudimentary leaves 
(bud scales) compactly arranged upon them. 
The plumule represents the first bud on the initial stem or caulicle. 
Scaly buds are such as have their outer leaf rudiments transformed 
into scales; there are often coated with a waxy or resinous substance 
without and a downy lining within, to protect them from sudden 
changes in climate. Buds of this character are common among 
shrubs and trees of temperate regions. 
Naked buds are those which are devoid of protective scales. 
They are common to herbaceous plants. 
Classification of Buds According to Development .—1. A leaf bud 
is a young shortened shoot bearing a number of small leaves. It is 
capable of elongating into a branch which bears leaves. 
2. A flower bud is a rudimentary shoot bearing one or more 
concealed and unexpanded young flowers. 
