first month of the year in the Julian and Gregorian calendars and the first month to have the length of 31 days.
 The first day of the month is known as New Year's Day.
 It is, on average, the coldest month of the year within most of the Northern Hemisphere (where it is the second month of winter) and the warmest month of the year within most of the Southern Hemisphere (where it is the second month of summer).
 In the Southern hemisphere, January is the seasonal equivalent of July in the Northern hemisphere and vice versa.
Haliclystus is a genus of stalked jellyfish that contains 11 species and one nomen nudum ("Haliclystus sanjuanensis").
 It is the largest genus of any in the order Stauromedusae.
 Members of this genus are found in the Pacific, Atlantic, Indian, Arctic, and Southern oceans.
 Two members of this genus, "Haliclystus kerguelensis" and "Haliclystus antarcticus", are found in the Southern hemisphere only.
 The remaining 9 members are found in the Northern hemisphere only.
June is the sixth month of the year in the Julian and Gregorian calendars and the second month to have the length of 30 days. June contains the summer solstice in the Northern Hemisphere, the day with the most daylight hours, and the winter solstice in the Southern Hemisphere, the day with the fewest daylight hours (excluding polar regions in both cases).
 June in the Northern Hemisphere is the seasonal equivalent to December in the Southern Hemisphere and vice versa.
 In the Northern hemisphere, the beginning of the traditional astronomical summer is 21 June (meteorological summer begins on 1 June).
 In the Southern hemisphere, meteorological winter begins on 1 June.
Cherax is the most widespread genus of fully aquatic crayfish in the Southern Hemisphere.
 Together with "Euastacus", it is also the largest crayfish genus in the Southern Hemisphere.
 Its members may be found in lakes, rivers and streams across most of Australia and New Guinea.
 In Australia the many species of "Cherax" are commonly known as yabbies.
 The most common and widely distributed species in Australia is the common yabby ("Cherax destructor").
 It is generally found in lowland rivers and streams, lakes, swamps and impoundments at low to medium altitude, largely within the Murray–Darling Basin.
 Common yabbies are found in many ephemeral waterways, and can survive dry conditions for long periods of time (at least several years) by aestivating (lying dormant) in burrows sunk deep into muddy creek and swamp beds.
Blechnum (hard fern) is a genus of between 150–220 species of ferns with a cosmopolitan distribution, in the family Blechnaceae in the eupolypods II clade of the order Polypodiales.
 By far the greatest species diversity is in tropical regions of the Southern Hemisphere, with only a few species reaching cool temperate latitudes in the Southern Hemisphere (notably "B. penna-marina", south to Cape Horn, Chile, the southernmost fern in the world) and Northern Hemisphere (notably "B. spicant", north to Iceland and northern Norway).
The Lilioideae are a subfamily of monocotyledon perennial, herbaceous mainly bulbous flowering plants in the Liliaceae (Lily) family.
 They are found predominantly in the temperate and colder regions of the Northern Hemisphere, particularly East Asia and North America.
 The subfamily includes two tribes.
 They are of economic importance, particularly the lilies and tulips.
Cortinarius violaceus, commonly known as the violet webcap or violet cort, is a fungus in the webcap genus "Cortinarius" native across the Northern Hemisphere.
 The fruit bodies are dark purple mushrooms with caps up to 15 cm across, sporting gills underneath.
 The stalk measures 6 to by 1 to , sometimes with a thicker base.
 The dark flesh has a smell reminiscent of cedar wood.
 Forming symbiotic (mycorrhizal) relationships with the roots of various plant species, "C. violaceus" is found predominantly in conifer forests in North America and deciduous forests in Europe.
The Galaxiidae, also known by the anglicised name as galaxiids, are a family of mostly small freshwater fish in the Southern Hemisphere.
 The majority of species live in Southern Australia or New Zealand, but some are found in South Africa, southern South America, Lord Howe Island, New Caledonia, and the Falkland Islands.
 One of the galaxiid species, the common galaxias ("Galaxias maculatus"), is probably the most widely naturally distributed freshwater fish in the Southern Hemisphere.
 They are coolwater species, found in temperate latitudes, with only one species known from subtropical habitats.
 Many specialise in living in cold, high-altitude upland rivers, streams, and lakes.
Acaena is a genus of about 100 species of mainly evergreen, creeping herbaceous perennial plants and subshrubs in the family Rosaceae, native mainly to the Southern Hemisphere, notably New Zealand, Australia and South America, but with a few species extending into the Northern Hemisphere, north to Hawaii ("A. exigua") and California ("A. pinnatifida").
Sparganium (bur-reed) is a genus of flowering plants, described as a genus by Linnaeus in 1753.
 It is widespread in wet areas in temperate regions of both the Northern and Southern Hemispheres.
 The plants are perennial marsh plants that can grow to 3.5 m (depending on the species), with epicene flowers.

Question: Which genus is found predominantly in the Southern Hemisphere, Acaena or Sparganium?
Answer: Acaena