404 



BOTANY 



is thus inaugurated. In perennial stems there are thus formed 

 regular growth-rings, like those of the Conifers. 



THE MATURE SPOROPHYTE 



The sporophyte in the Dicotyledons varies extremely in size and 

 complexity. Sometimes it is a delicate annual herb, living but a 

 few weeks or months, while on the 

 other hand it may be a gigantic tree 

 living for many centuries. Some of 

 the parasitic and aquatic Dicotyledons 

 (e.g. Rafflesiacese, Podostemonaceae) 

 are thallose plants, without any clearly 

 marked external organs, aside from 

 the flowers. While aquatic forms are 

 less frequent than among Monocoty- 

 ledons, some genera, like Utricularia, 

 Ceratophyllum, and Myriophyllum, 

 are characteristic submersed aquatics. 

 Xerophytes, or forms adapted to dry 

 conditions, are numerous, some of the 

 xerophytic types, like the Cacti, and 

 some Euphorbias, being especially per- 

 fect instances. Parasites , and sapro- 

 phytes are common, and in the Tropics 



FIG. 381. Hippuris vulgaris. Stem-apex, 

 showing the primary tissues ; e, epi- 

 dermis; p, p, plerome; pb, periblem. 

 (After DE BARY.) 



FIG. 382. Clematis viticella. Dia- 

 gram to show the arrangement 

 of the vascular bundles. (After 

 NAGKLI.) 



many epiphytic and climbing Dicotyledons abound. One peculiar 

 order (Sarraceniales) is noteworthy for the curious contrivances 

 developed for entrapping insects and similar small animals. In 

 short, among the Dicotyledons is to be found almost every type of 

 plant-structure. 



