In the Araceae, the individual flowers are small and inconspicuous (as you will see shortly, it is the inflorecences that is conspicuous). The flowers may be perfect or imperfect, and the latter case the plants may be monoecious or dioecious. The number of sepals and petals vary from zero to three, and there the number of stamens is also variable. The gynoecium is syncarpous from 2 to 4 carpels, and the ovary is superior. Araceae 02 Introduction 02-Introduction The Araceae is a very widely distributed family. While some members are found in temperate regions, especially the genus Arisaema, the family is most diverse in the tropics. Araceae 03 Leaves 03-Leaves Note that the leaves in this family often have reticulate venation rather than parallel venation, which is typical of most monocots. Also, the plants often contain sharp crystals of calcium oxalate and are thus poisonous. Photo taken by K. R. Robertson the Missouri Botanical Garden, St. Louis. Araceae 04 Habit 04-Habit The habit of Araceae is quite varied — some are climbers, others are epiphytes, others are terrestrial, and a few are even aquatic. Araceae 05 Inflorescences 5-Inflorescences The inflorescence has a distinctive structure in this family — there is a SPATHE or sterile leaf below or sheathing around a SPADIX, a cylindrical structure that bears flowers at the base. Araceae 06 Inflorescence 06-Inflorescence This photo is of an inflorescence of Aglaconema modestum and it shows the green spathe and the white spadix, which is covered with flowers. White male flowers cover most of the spadix and only a few female flowers are found at the base. Photo by KRR and D.L. Nickrent from plants cultivated at the University of Illinois. Araceae 07 Arisaema habit 07-Arisaema habit A common spring woodland wildflower in Illinois is Arisaema triphyllum, Jack-in-the-pulpit. The spathe (or the "pulpit") forms a hooded sheath around the spadix (or the "Jack"). The inside of the spathe sometimes has reddish-brown stripes on the inside. Araceae 08 Arisaema inflorescences 08-Arisaema inflorescence In this photograph are the spathes from two different plants of Jack-in-the-pulpit (Arisaema triphyllum) that have been partially cup open to show the structure. Inside each spathe is a spadix - the one on the left having female flowers and the one on the right with male flowers. Note that in this genus the spadix has a large sterile appendix, with the flowers confined to the lowermost part. Araceae 09 Arisaema fruit 09-Arisaema fruit he fruit in the Araceae is usually a berry, as in Jack-in-the-pulpit, Arisaema triphyllum. Since there are numerous separate flowers on one spadix, there are numerous berries. So, what you see here is a multiple fruit of berries. Araceae 10 Amorphophallus 10-Amorphophallus The giant inflorescences are sometimes called the "world's largest flower". However, this is an inflorescence, not a flower; as you will recall from the lecture on parasitic plants, the largest flower is produced by Rafflesia arnoldii.
Nevertheless, this does not make the inflorescences of Amorphophallus titanum any less impressive! In the photo on the right is a famous early geneticist Hugo de Vries standing on an oil barrel alongside an inflorescence at the New York Botanical Garden. The photo on the left was of a plant in bloom at Kew Gardens in London, England. The very large spathe is brown on the inside, indicating that this is a carrion flower (i.e., they small awful!). The spadix is green and cylindrical. Araceae 11 Anthurium spathe 11-Anthurium spathe With the bright red spathe and yellow spadix, many Anthriums are cultivated for use in the florist trade. Photo by K. R. Robertson in Jamaica. Araceae 12 Pink Anthurium 12-Pink Anthurium A common Araceae in the florist trade is the genus Anthurium, which has colorful spathes. This is a large genus of lianas that is widespread in tropical regions. Photo taken by K. R. Robertson in Jamaica. Araceae 13 Caladium 13-Caladium Caladium bicolor is commonly cultivated for the large, colorful leaves. This species is native to tropical America. Photo taken by K. R. Robertson at the Missouri Botanical Garden, St. Louis. Araceae 14 Colocasia 14-Colocasia habit The leaves of Colocasia antiquorum, taro, are very large, usually more than 2 feet long. The underground corms are high starch and are an important food crop in some tropical regions. Photo by K. R. Robertson in Fairchild Tropical Garden. Araceae 15 Monstera 15-Monstera Often seen in shopping malls and office building is Monstera deliciosa, or split-leaf philodendron. The spathes can be 1 foot long! The fully ripe fruit is edible, creamy-smooth, and like a custard. The flavor has been described as reminiscent of pineapple with touches of banana and mango. The unripe fruit will inflame the mouth and throat because of the calcium oxalate crystals. Photo by K. R. Robertson at the Missouri Botanical Garden. Araceae 16 Philodendron 16-Philodendron Numerous species of Philodendron and Aglaonema are cultivated outdoors in tropical regions. Some are also grown in greenhouses and as house plants. Photo by K. R. Robertson in Jamaica. Araceae 17 Pistia 17-Pistia One curious member of the Araceae is water lettuce, Pistia stratiotes, a floating aquatic plant found in tropical regions. The plants are up to a foot in diameter and are a favorite food of manatees in Florida. In the very center of this plant you can see a small spathe enclosing a spadix. Photo by K. R. Robertson of plants cultivated in Champaign, Illinois. Araceae 18 Symplocarpus spathes 18-Symplocarpus Skunk cabbage, Symplocarpus foetidus, is a spring wildflower that is only found in wet, calcareous areas, such as seeps and the edges of springs. Like certain other Araceae, skunk cabbage can carry out a high enough rate of metabolism to produce heat! The spathes are warm enough to melt their way through the snow. Photo by Robert A. Evers, botanist for many years with the Illinois Natural History Survey. Araceae 19 Symplocarpus spathe 19-Symplocarpus spathe This shows a spathe of Skunk cabbage, Symplocarpus foetidus, in longitudinal section. The round spadix of male flowers can be see in the center. Photo by K. R. Robertson from plants near Carlisle, Pennsylvania. Araceae 20 Symplocarpus fruits 20-Symplocarpus fruits The fruits of skunk cabbage mature in the fall, and they are multiple fruits with the berries and seeds embedded in the spongy spadix. Photo taken by K. R. Robertson at Trout Park Nature Preserve, Kane County, Illinois. Araceae 21 Symplocarpus leaves 21-Symplocarpus leaves During the summer months, the large, bright green leaves of skunk cabbage can be seen in wet areas. Photo by K. R. Robertson at Bennett's Terraqueous Gardens Nature Preserve, Tazewell County, Illinois. Araceae 22 Zantedeschia aethiopica 22-Zantedeschia aethiopica Calla lilies, Zantedeschia aethiopica, are commonly used in the florist trade for the graceful white spathes that surrounds a yellow spadix.