604 JOURNAL OF TIIE ROYAL HORTICULTURAL SOCIETY. 



it seems that it now cannot start into growth without the stimulus excited 

 by the endophyte. 



This appears to account for the difficulty florists experience, and the 

 right course to pursue is to sow the seed on soil taken from the pot in 

 which the same species had heen grown for some time, as the soil will 

 have become thoroughly impregnated with the particular species of Fusi- 

 sporium required. 



So important is it believed to be that tubers cannot be formed unless 

 the plant has been entered by the fungus through the roots beforehand. 

 This not only applies to Orchids, but the Lesser Celandine and even 

 Potatos. Experiments appear to show that if the fungus is withheld the 

 underground shoots of the Potato are merely prolonged without their 

 forming tubers at all.* 



Parasitic and Saprophytic Roots. — Many flowering plants have 

 acquired the property of attaching themselves to the roots of others and 

 thereby extracting nourishment from them. They thus become parasitic. 

 There is every degree between a perfect parasite which has lost all power, 

 of making starch, by having no green leaves or chlorophyll, and a plant 

 with green leaves capable of supporting itself, yet having the power to 

 become a parasite. Thus, while Broom-Rapes (Orobanche sp.) cannot live 

 apart from a host-plant, the parasitic Cow- Wheat (Mclampyrum pratense) 

 can not only be a saprophyte as well — that is, nourish itself in decayed 

 organic matter — but be independent of either means of support, though it 

 has been discovered that its power of assimilating the carbonic acid of the 

 air, and thereby making starch, is much enfeebled by its having acquired 

 a parasitic habit. 



The means by which a parasitic plant becomes attached to the host- 

 plant begins with a growth in the epidermis and underlying cortical 

 tissue, this being excited by the contact and then by multiplying the cells 

 till a sort of pad is formed and applied to the root of the host-plant. 

 Then vessels (tracheids) are formed extending from those of the root 

 down the middle of this pad-like " sucker " till they reach and unite with 

 the vessels of the root of the host-plant, and so the connection is effected 

 and nourishment is drawn up into the parasite. 



Saprophytes are plants which, as a rule, have no true and really green 

 leaves, but live on decayed vegetable matters in the soil. As all plants 

 do this, they are in a way saprophytic, but having retained their green 

 leaves are not so called ; moreover, they can assimilate carbonic acid. As 

 an example is the common Bird's-nest Orchis (Ncottia Nidus-avis), which 

 is found in the dead foliage of Beech woods. The rhizome of this plant 

 abounds with an endophytic fungus. 



Epiphytic Roots. — Both the preceding must be distinguished from 

 epiphytes, whose roots only cling to the external support, such as rocks, 

 trees, &c, but derive no nourishment from them. 



Thus tropical Orchids have long roots of a peculiar kind, the epidermal 



* The above discovery appears to require confirmation as far as all tubers are 

 concerned, for tubers may be formed in the axils of the leaves of the plants, and it is 

 not clear how these could be infected by the fungus. The reader is referred to a 

 .series of papers in Rev. Gi'n. dc Botanique, 1902. 



