Lecture V 

 DISTRIBUTION OF MYCOTROPHIC PLANTS 



General: — It is unknown whether plants in nature have root- 

 hairs or mycorrhizae,— -or neither; but there is enough evidence at 

 hand to indicate that mycorrhizae predominate over root-hairs in the 

 majority of cases. That many plants can produce root-hairs when 

 grown under artificial conditions of greenhouse or laboratory control 

 has been amply demonstrated, yet it is also demonstrated that these 

 same species of plants when in their native haunts may produce mycor- 

 rhizae. Hence, almost exclusive study of root-hair plants in botanical 

 classwork is questionably scientific, and some day Botany must revise 

 its programme; for the attitude of traditionalism that has fastened 

 itself upon Science is unfortunate. In the future, the Geograph- 

 ical Distribution of root structures will doubtless be better known; 

 but at present something of a picture of mycorrhizal distribution may 

 be gained from incidental references made in various papers. There 

 are very few researches that deal directly with the subject. 



Two general observations may be noted before the geographical 

 data are presented. First, Costantin & Magrou (1926) thought 

 that geographical distribution of symbiotic plants depends on distri- 

 bution of mycorrhizal fungi: Thus, mountain plants rest ephemerally 

 on the plains because of absence of appropriate fungi. But this idea 

 is not very well established and awaits further evidence. Second, 

 WiLKiNs & Patrick (1939) thought that "there is a possibility that 

 the phanerogamic species may influence fungus distribution." This 

 idea is perhaps better grounded than the former. 



Since more than one half the students of our science have lived 

 in western Europe, more is naturally known of mycorrhizae in this 

 region than in the rest of the world. 



Germany: — Botanists of Germany, earliest and chief center of 

 mycorrhizal study, have given us records of a large part of the German 

 flora. Chief among these studies are those of Schlicht (1888), a 

 student of Frank. He was led to investigate herbs of his region by 

 finding mycorrhizae on Rammculus acris and he came to the con- 

 clusion that mycorrhizae are "distributed over a great range of our 

 flora." His reports form an almost unique model for in each case he 



