70 ANCIENT PLANTS 



Stigmaria is only introduced as an example, one of 

 the very few available, of a palaeozoic structure which 

 seems to be of a nature not clearly determinable as 

 either root, stem, leaf, or fructification. Among living 

 plants the fine rootlike rhizophores of Selaginella bear 

 some resemblance to Stigmaria in essentials, though so 

 widely different from them in many ways, and they 

 are probably the closest analogy to be found among 

 the plants of to-day. 



The individual cells, we have already seen, are 

 strikingly similar in the case of 

 fossil and living plants. There 

 are, of course, specific varieties 

 peculiar to the fossils, of which 

 perhaps the most striking seem to 

 be some forms of hair cells. For 

 example, in a species of fern from 

 the French rocks there were mul- 

 ticellular hairs which looked like 

 little stems of Equisetum owing 

 to regular bands of teeth at the 



Fig. 48. — Stele of Lepidoden- • . • r . 1 11 /-rii 1 



dron w, surrounded by a small junctions ot the cells. _ I hese hairs 

 ring of secondary wood s Were quite characteristic of the 



species — but hairs of all sorts 

 have always abounded in variety, so that such distinction 

 has but minor significance. 



As was noted in the table (p. 58) the only cell types 

 of prime importance which were not evolved by the 

 Palaeozoic plants were the wood vessels, phloem and 

 accompanying cells which are characteristic of the 

 flowering plants. 



Among the fossils the vascular arrangements are 

 most interesting, and, as well as all the types of stele 

 development noted in the previous chapter as common 

 to both living and fossil plants, there are further varieties 

 found only among the fossils (see fig. 50). 



The simple protostele described (on p. 61) is still 

 found, particularly in the very young stages of living 



