FAMILIES OF FLOWERING PLANTS 153 
small aquatic or sometimes terrestrial herbs, comprised in the single 
genus Callitriche, which contains about 20 widely distributed species. 
They have slender stems, opposite leaves, and minute perfect or monoe- 
cious axillary flowers, destitute of calyx and corolla; stamen one, ovary 
4-celled, becoming a capsular fruit which splits into 4 little one-seeded 
carpels. The plants are inconspicuous, and without special interest. 
Fig. 132. Allegheny Mountain spurge (Pachysandra procumbens). Original. 
CHAPTER XXIII. 
Order Sapindales. 
This order is essentially similar to the Geraniales, although there 
are important differences in the structure of the seed, The families 
comprised in it must therefore be learned by experience. There are 
20 of these, the most important being the Anacardiaceae, Aquifoliaceae, 
‘Celastraceae, Aceraceae, Hippocastanaceae, and Sapindaceae. 
