LIFE OF AN ORCHID 25 



fig. 6, 6), almost as broad as the tuber, both furnished with absorbent hairs, which 

 pushes the tuber beneath the soil. The latter has several steles and is free from endo- 

 phytes. Adventitious roots (Text-fig. 6, 10) are put forth above the tuber, which 

 grow horizontally or obhquely, and become infected with mycorrliiza from the soil. 

 Each year a stronger tuber is produced, and the old one shrivels away, gradually how- 

 ever, for sometimes the remains of two decaying tubers are found. The young plant 

 grows vegetatively from 4 to 7 years (much longer in some exotic genera), building 

 up a larger store of nutriment, till at length it is able to flower. A few species normally 

 put forth two new tubers yearly, e.g. Herminium tmnorchis (which sometimes has 

 2-5 new tubers), Ophrys bombjiiflora, Serapias gregaria, etc. This also sometimes 

 happens with unusually vigorous plants of other genera, e.g. Orchis mascula. 



The protocorm is at first almost globular, less than \ mm. long, and hes on its 

 side, except in Cypripedium, in wliich it is erect. Text-fig. 6, // shows a section of 

 a magnified protocorm of Orchis militaris; B. is the bud, Sl the stele, and the dots 

 show the area invaded by the fungus (after Irmisch). 12 is 2. section of a plantlet 

 of 'Platanthera chkrantha, P. protocorm, T. tuber of second year; 13 shows a still 

 more enlarged section of another plant of the same species in May (after Bernard). 

 In Text-fig. 6, 2 shows bud developing; 2 a, first sign of new tuber; 3, development 

 of the latter; 4, appearance of roots; 5, protocorm slirivelling ; 6, plant of third year 

 with tiny new tuber at tip of a stalk; 7, the latter full grown, and old tuber shrivelling 

 up; 8, section of bud in autumn with rudimentary flower-spike visible; 5, plant about 

 January (south of France), old tuber gone, new tuber (T.) beginning ;'/o, the same 

 in May or June, old tuber withering and the new well developed ; 14, seedhng in June, 

 p. protocorm, /. first tuber, st. stalk, sh. sheath, /. first leaf. 



Bletiiia hjacinthina of Eastern Asia can germinate either with or without fungus, 

 but in the latter case no bulb is formed.' Although it is possible to induce germination 

 on richly nutritive media, the only method in nature appears to be fungal invasion. 

 It is said that very rarely the fungus invades the whole plant and destroys it, but 

 normaUy it is confined to the limited areas where its presence is beneficial.^' As 

 Cynips produces galls on a leaf, so perhaps invasion of an orcliid by a fungus gives 

 rise to the tuber.3 



Cypripedium increases by annual zigzag growths of the rhizome, wliich is usually 

 free from fungus, the roots only being infected. Irmisch figures a plant wloich has 

 had six annual growths without being yet strong enough to flower.4 Cephalanthera 

 rubra m loose, calcareous soil is sometimes found with branched roots, the older ones 



■ Weiss, "Seeds and seedlings of Orchids", Trans. Manchester Micros. Soc. fiqiy) 



2 Camus, Icon. pp. 32, 35, 47. ^ ■' "' 



3 Constantin, L,a vie des Orchide'es, p. 155. 



t Irmisch, Beitrdge ^ur Biokgie und Morphologie der Orchideen. 



