Kelley — 16 — Mycotrophy 



water; while Hales (1727), no less than the Father of Plant Physi- 

 ology !, decided that root-hairs are only incidental phenomena in intake 

 of materials from the soil, the chief intake being through the root tips. 

 Among the seemingly countless authors of the first 20 years of the 

 19th century (yet producing nothing new), may be mentioned Garra- 

 DORi and MoLDENHAWER. The former noted that root-hairs are 

 wanting in water, from which he concluded that they serve, not for 

 absorption of liquid water, but moisture from the air, while liquid 

 water is taken up by spongy root-ends. According to Moldenhawer, 

 root-hairs may be compared tO' druse-hairs of leaves : they secrete a 

 liquid which serves to dissolve the food materials, being comparable 

 in a way to saliva of animals. 



The first description that was given right direction was by F. 

 Meyen {in Neues System der Pflanzenphysiologie, 1838. Bd. 2, p. 

 6), who proceeded from a description of absorptive hairs of moss and 

 characeous plants, showing incidentally that in these cases the root- 

 hairs completely take the place of roots. He called attention further- 

 more to the supposed universal distribution of root-hairs in higher 

 plants, investigated their development, and what is more important, 

 attributed to them the direct intake of liquid water. He came to the 

 view that root-hairs serve merely to increase the outer surface of the 

 root, and he showed that the number of root-hairs formed is dependent 

 upon external conditions. Next we may cite the work of G. Gaspar- 

 RiNi, the "Richerche sulla natura dei succiatori e la escrizione delle 

 radici" (1856), which is a most comprehensive work on root-hairs 

 but it offers in general nothing new. Gasparrini had investigated 

 quite a large number of plants and found them with few exceptions to 

 have root-hairs ; he did not go into a study of the conditions of root- 

 hair formation but satisfied himself with describing their form, con- 

 tent, etc. The finest portions of earth, embedded in a gummy sort of 

 a mass which clung to the root-hairs he considered to be excretionary 

 products of the hairs. He even designated as such roots which had 

 an evident root-cap. Schacht incorporated Gasparrini's work in 

 his text of 1859. Much more precise than his predecessors, Sachs 

 (1860) made clear the significance and function of root-hairs; and 

 from him the more modern phases of such study may be dated. 



Generality of Mycorrhlzal Occurrence: — In spite of our 

 comparative ignorance of root structure in particular, it is known that 

 in all major groups in the plant kingdom there are fungi living with 

 other plants in mutualistic relation. No major group from "Thallo- 

 phyte" to Spermatophyte is excepted. In the lower groups we speak 

 of mycothalli or lichen bodies while in higher groups are mycorrhizo- 



