400 Proceedings Portland Society Natural History 



and the numerous rotten logs, but extend well up the base 

 of the trees. Conspicuous forms are : 



Bazzania trilobata Climacium americanum 



Trichocolea tomcntclla Mnium punctatum 



Kiccardia latifrons Thuidium delicatulum 



Ptilium crista-castrensis Hylac omnium splendens 



Calliergon cordifolium Ptilidium pulcherrimum 



Rhytidiadelphus triquetrus Stereodon cupressifor-mis 



Other genera, such as Lepidozia, Lophocolea, Sphagnum, 

 Cephalozia, Dicranum and Chrysoliypnum are also frequent, 

 as are several lichens, chiefly Peltigera, Lobaria and Usnea. 



Characteristic herbaceous species include: 



Dryopteris Thelypteris Cypripedium hirsutum 



Osmunda cinnamomea Coptis trifolia 



Carex flava Drosera rotundifolia 



Carex trisperma Viola incognita 



Symplocarpus foetid us Chiogenes hispidula 



Smilacina trifolia Mitchella rcpens 



b. Association-types of periodic lakes and ponds 



Periodic ponds are more closely allied to well-drained 

 than to undrained areas, since the drying out which they 

 undergo during the summer accomplishes essentially the 

 same result as might otherwise be effected by drainage. 

 The vegetation in these periodic ponds differs from that of 

 permanent ponds chiefly in the absence of the aquatic forms. 

 Water is present for too short a period for these to de- 

 velop and swampy conditions prevail almost from the out- 

 set. The most characteristic species in these "bog-holes" 

 which occupy mucky depressions in fields and pastures, is 

 the cat-tail (Figure 35) and with it are found: 



Sparganium diversifolium J uncus effusus var. Pylaei 



Glyceria nervata Juncus brevicaudatus 



Eleocharis obtusa Hypericum virginicum 



Eleocharis tenuis Lysimachia terrestris 



