ANGIOSPERM^ 



389 



rium, are climbers, reaching to the tops of trees, and are among the most 

 characteristic of all plants. Monstera deliciosa, with its big perforate leaves, 

 is familiar in conservatories. 



The flowers of the Aracese show a good deal of variety. In the simplest forms, 

 e.g. Aglaonema, Spathicarpa, the flowers consist of a single carpel, with a basal 

 ovule, or of a single stamen. In others, e.g. Anthurium, Lysichiton, there is a 

 compound ovary, and the flowers are hermaphrodite, with a rudimentary peri- 

 anth. The flowers may be confined to the base of the spadix (Arissema), or 

 they may cover it completely (Symplocarpus). The inflorescence sometimes 

 reaches an enormous size. In AmorpTiophallus titanum, the spathe is nearly a 

 metre in length. In these large forms the evolution of heat by the inflorescence 

 is very marked, and a thermometer thrust into the spathe, especially at the time 

 that the pollen is being shed, indicates a much higher temperature than that of 

 the surrounding atmosphere. In Philodendron melanochrysum, an East Indian 



sp 



FIG. 363. A, Spathicarpa sagittasfolia, the simple flowers attached to the leaf- 

 like spathe, sp (X i). B, staminate, I, and pistillate, II, flowers, enlarged. 

 C, leaf of Arissema triphyllum (X i). D, Nephthytis Llberica, fruits (X |). 



species, Kraus found a maximum difference of 12.6 C. This took place in the 

 evening, and was accompanied by an increase hi the odor, which is often very 

 pronounced in these plants. The biological significance of this rise in temperature 

 Kraus considers to be the attraction of insects, which seek shelter in the warm 

 spathe, and thus receive the pollen, which they afterward carry to another inflo- 

 rescence. The odor of many Aracese is extremely offensive, and the colors dull. 

 Such forms attract carrion-insects, which serve to pollinate them. 



Histology. The tissues of the Aracese usually contain numerous needle- 

 shaped crystals, or rhaphides, to which has been attributed the extremely acrid 

 taste of many of them. Some of them (Dieffenbachia seguine) possess a milky 

 juice, which is said to be extremely poisonous. 



Fam. 2. Lemnaceae. The very much reduced plants, the Lemnaceae (Fig. 

 365), are related to the Aracese, and are sometimes included with them. Lemna 

 has roots, Wolffia is rootless. The latter is the smallest of all vascular plants, 



