What's the difference between genus and horseweed?

Genus

Definition:

(n.) A class of objects divided into several subordinate species; a class more extensive than a species; a precisely defined and exactly divided class; one of the five predicable conceptions, or sorts of terms.
(n.) An assemblage of species, having so many fundamental points of structure in common, that in the judgment of competent scientists, they may receive a common substantive name. A genus is not necessarily the lowest definable group of species, for it may often be divided into several subgenera. In proportion as its definition is exact, it is natural genus; if its definition can not be made clear, it is more or less an artificial genus.

Example Sentences:

(1) The genome characterization of the typing strains for all 13 species of the genus Staphylococcus, included into the Approval List of the Names of Bacterial (1980), is presented.
(2) The genus Streptomyces was dominant in the two studied localities.
(3) The compounds favored the development of bacteria of the genus Pseudomonas and inhibited the growth of all other gram-negative bacteria.
(4) Organisms of the genus Bacteroides represent the major group of obligate anaerobes involved in human infections.
(5) The 212 strains of this proposed subserovar examined to date display biochemical and serological properties typical of the species, are sensitive to the genus-specific bacteriophage, and cause keratoconjunctivitis in the Sereny test.
(6) The new species has been placed in a new genus and the name Tricornia muhezae proposed.
(7) Although differing somewhat in their responses to various biochemical and biophysical tests, all strains were assigned to the genus Flavobacterium.
(8) Ten TBT-resistant isolates from estuarine sediments and 19 from freshwater sediments were identified to the genus level.
(9) A new genus of actinomycetes, Excellospora Agre a. Guzeva gen. nov., is suggested on the basis of this study.
(10) A new genus of spirochaetes, Hollandina, is also described.
(11) The first group consisted of all strains belonging to L. interrogans and serovar andamana of L. biflexa; the second group consisted of the remaining 5 serovars of L. biflexa; the third group consisted of the genus Leptonema; and the fourth group consisted of only L. parva.
(12) The reservosomes of Trypanosoma spp., sub-genus Schizotrypanum, could be differentiated from the multivesicular bodies of other trypanosomatids, since they lack true vesicles.
(13) Statistical analysis of 251 phylogenetically informative nucleotide positions rejects the "volvocine lineage" hypothesis, which postulates a monophyletic evolutionary progression from unicellular organisms (such as Chlamydomonas), through colonial organisms (e.g., Gonium, Pandorina, Eudorina, and Pleodorina) demonstrating increasing size, cell number, and tendency toward cellular differentiation, to multicellular organisms having fully differentiated somatic and reproductive cells (in the genus Volvox).
(14) In all cases, the determinants of the killer trait are carried by obligate bacterial endosymbionts belonging to the genus Caedibacter.
(15) Lastly, the CVA indicated major differences across the genus to be located in the teeth and jaws, suggesting diet might be an important distinguishing feature in Colobus.
(16) Another pigment 7 was specifically present in the skin of genus Rhacophorus and was deduced to be a pteridine derivative composed of five molecules of pterin-6-carboxylic acid [1].
(17) Bacteria of the genus Thiobacillus can obtain energy from the chemolithotrophic oxidation of inorganic sulphur and its compounds (sulphide, thiosulphate and polythionates) and use this energy to support autotrophic growth on carbon dioxide.
(18) A platelet-aggregating activity was found in many snake venoms, predominantly those of the genus Bothrops, that is apparent only in the presence of the platelet-aggregating von Willebrand factor of plasma.
(19) Sporobolomyces yuccicola is the sixth species of the intermedius group, a group of atypical species of the genus Sporobolomyces equipped with Q-9.
(20) This reduction was confined to strict anaerobes, mainly the genus Eubacterium and Bifidobacterium.