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Darwin Correspondence Project

From Francis Darwin   [after 2 June 1879]1

Dear Father,

Here is an abstract about the firs: Stahl says it is impossible to be certain about your piece of wood but he thinks a little fir tree growing on a branch out of such a lump can be nothing but the Hexenbesen; there is mycelium in the wood you sent but that alone is not enough.2 He says there are lots of affected trees near Strassbourg & he could easily send us a young tree with a hexenbesen on it in the autumn. Have you noticed the young shoots of scotch fir how vertically they grow up, while spruce buds curve downwards slightly like hazel buds. The Finlander is experimenting on the horizontal underground shoots of Scirpus &c & finds they have just the same instinct to grow horizontally as an ordinary shoot has to grow vertically—which is the much abused “transversal-geotropismus” of Frank only his transvers: geotr was with above ground things which are affected by light—3 I will ask more about Krause— Stahl who is not usually severe called him an “abscheulicher Mensch” but Stahl as 12 French hates Berliners: every one hates Kosmos I think as the organ of “uncultivated materialism”—4

Hermann Müller has been christened Kohlenstoff Müller because he was complained of for teaching the boys in school that they should not believe “in the beginning was the word” but “in the beginning was Carbon”!5

I have got two good Porlieras in a room where I can do what I like & I will keep one in damp earth & one in dry &c & make careful observns.6 I am very glad you are done with old Eras7

I am very sorry about poor Jimmys pit & also for Pouts’ horse8 yrs affec | FD


Bot Zeitung 1867 p257

A de Bary Ueber den Krebs und die Hexenbesen der Weisstanne Abies pectinata9

The Krebs consists of a lump on the stem or branches, the swelling is about twice the diameter of the stem above & below it. Remarkable for very thick bark which is externally deeply cracked. Ultimately the bark comes off the & wood rots extensively. The wood & especially bark is crowed with mycelium which is continued into the branches that grow out of the swellings & reproduces itself in the young leaves. The branches growing out of the swellings are the little upright trees or Hexenbesen. He speaks also of hexenbesen growing out of the stem— {for Hexenbesen he quotes De Bary Ann Sc Nat 4 Sér, Tom XX p 90}.10 The fungus is Æcidium elatinum:11 he speaks of the mycelium growing from a swelling into “side branches” without producing reproductive organs, which latter are only in the true hexenbesen. The hexenbesen is only formed when the mycelium grows from the swelling into a bud beginning to elongate   If it grows into already unfolded though still young shoots it does not produce a hexenbesen, only another swelling   One and the same swelling may produce hexenbesen and normal branches   Normal shoots free from mycel may come from hexenbesen. The hexenbesen are found all over the tree, most rarely at the summit of a young tree. The hexenbesen-shoots may either grow from the very first vertically up, or bend upwards with a bent piece. The first year they are simple shoots, & form a winter bud at the top. The branches which grow from the main hexenbesen axis are like the primary branches of a young fir tree & grow out on all sides


The leaves fall off in autumn & are rather smaller than normal, “Krautartig-fleischig”12 & light yellow green in colour. If the fungus does not fructify which is very rare they the leaves live over the winter   “The hexenbesen sits on the branches like a strange looking bush in winter bare, in summer light green”   Imitating a a little fir tree if it grows regularly or looking like a confused bush if it has grown irregularly. The hexenbesen are usually more regular in growth when only one grows out of a swelling. They usually die in a few years but may live in one case 16 years   In the hexenbesen, as in the swellings, the bark is very thick. “Very rarely one finds side shoots on the hexenbesen free from mycelium which then assume all the properties of normal fir branches”13

(I dont understand this as I thought the side branches of the hexenbesen were always like normal branches of a young fir tree. F D)

CD annotations

1.4 He … Pouts’ horse 4.1] crossed blue crayon
3.12 bud … elongate] underl red crayon


The date is established by the relationship between this letter and the letter to Francis Darwin, 2 June [1879].
CD had sent Francis a twig of Abies pectinata (a synonym of A. alba, silver fir) with a small swelling (see letter to Francis Darwin, 2 June [1879]). Ernst Stahl, an assistant of Julius Sachs at Würzburg, had worked on lichens and experimentally demonstrated their fungal character (see Cittadino 1990, pp. 83–4). Hexenbesen: witches’ broom (German); a clump of densely branched small shoots that can result from various tree parasites, such as fungi, mistletoe, insects, or viruses (for more on the cause of witches’ broom in silver firs, see Schweingruber 2007, pp. 215–18). Mycelium is the vegetative part of a fungus, characterised by fine branching threads or hyphae.
Scotch fir (Scots pine) is Pinus sylvestris; spruce trees are in the genus Picea. Fredrik Elfving was studying a problem suggested to him by Sachs, the tendency of the rhizomes of many plants to take up a horizontal position in the ground (Collander 1965, p. 44). Scirpus is the genus of bulrushes. Albert Bernhard Frank had proposed that there were special forms of growth in plant organs, characterised by an inherent tendency to be horizontal or to be placed at a right angle to the direction of gravity or a light source; he referred to these as ‘Transversal-Geotropismus’ and ‘Transversal-Heliotropismus’ (Frank 1870, p. 77). Frank’s thesis had been challenged by Hugo de Vries, who argued the phenomenon could be explained as a sort of equilibrium between opposing heliotropic and geotropic forces in conjunction with epinastic and hyponastic movements (the bending down and up of an organ due to greater longitudinal growth on one side; Vries 1872, p. 277). Frank had responded to De Vries’s criticisms with a more detailed experimental study of differences in movement that resulted from different tropic forces (Frank 1873).
Abscheulicher Mensch: odious man (German). Ernst Krause was the editor of the journal Kosmos, which promoted an evolutionary perspective in natural science.
Kohlenstoff: carbon (German). Hermann Müller was a senior teacher of natural sciences at the Realschule in Lippstadt. Müller had briefly explained the case in a letter to CD and sent two articles written by Krause in his own and Müller’s defence (see letter from Hermann Müller, 14 February 1879 and n. 3).
On the identification of plants as Porliera hygrometrica, see letter from Francis Darwin, 29 May 1879 and n. 3. In 1878, Francis had noted changes in movement that seemed dependent on the amount of water a specimen received (see Correspondence vol. 26, letter from Francis Darwin, [after 7 July 1878] and n. 3).
See letter to Francis Darwin, 2 June [1879]. CD had spent several weeks working on a biographical sketch to introduce an English translation of Ernst Krause’s essay on Erasmus Darwin (Krause 1879a). The translation appeared in November 1879 (Erasmus Darwin).
Jimmy was a nickname for Horace Darwin; Pout was a nickname for Leonard Darwin. The pit and the horse have not been identified.
Anton de Bary’s paper ‘Ueber den Krebs und die Hexenbesen der Weisstanne (Abies pectinata DC.)’ (On the canker and witches’ brooms of the silver fir (Abies pectinata DC.); Bary 1867) identified Aecidium elatinum (a synonym of Melampsorella caryophyllacearum, fir broom rust) as the pathogen that caused cankers and brooms in Abies pectinata (a synonym of Abies alba, silver fir) and described the progression of disease in infected trees.
See Bary 1867, p. 260; Bary referred to his paper in the Annales des sciences naturelles, ‘Recherches sur le développement de quelque champignons parasites’ (Researches on the development of some parasitic fungi; Bary 1863). Bary noted that it was probable that in certain members of the Uredinales (the order to which Aecidium elatinum belonged) the fungus alternately infested two types of host (Bary 1863, pp. 90–1).
See n. 9, above.
Krautartig-fleischig: herbaceous-fleshy (German); see Bary 1867, p. 262.
See Bary 1867, p. 262. Bary noted that the infected needles of a witches’ broom were small, yellow, herbaceous-fleshy, and shed in late autumn, but in rare cases when the fungus had not fructified the branches might have normal needles.


Bary, Anton de. 1863. Recherches sur le développement de quelques champignons parasites. Annales des sciences naturelles (botanique) 4th ser. 20: 5–148.

Bary, Anton de. 1867. Ueber den Krebs und die Hexenbesen der Weisstanne (Abies pectinata DC.). Botanische Zeitung 25: 257–64.

Cittadino, Eugene. 1990. Nature as the laboratory. Darwinian plant ecology in the German Empire, 1880–1900. Cambridge: Cambridge University Press.

Collander, Runar. 1965. The history of botany in Finland, 1828–1918. Translated by David Barrett. Helsinki: [Finnish Society of Sciences].

Erasmus Darwin. By Ernst Krause. Translated from the German by W. S. Dallas, with a preliminary notice by Charles Darwin. London: John Murray. 1879.

Frank, Albert Bernhard. 1870. Die natürliche wagerechte Richtung von Pflanzentheilen und ihre Abhängigkeit vom Lichte und von der Gravitation. Leipzig: Weissbach.

Frank, Albert Bernhard. 1873. Zur Frage über den Transversalgeotropismus und -Heliotropismus. Botanische Zeitung 31: 17–23; 33–9; 49–57.

Krause, Ernst. 1879a. Erasmus Darwin, der Großvater und Vorkämpfer Charles Darwin’s: ein Beitrag zur Geschichte der Descendenz-Theorie. Kosmos 4 (1878–9): 397–424.

Schweingruber, Fritz Hans. 2007. Wood structure and environment. Berlin and Heidelberg: Springer Verlag.

Vries, Hugo de. 1872. Ueber einige Ursachen der Richtung bilateralsymmetrischer Pflanzentheile. Arbeiten des botanischen Instituts in Würzburg 1 (1871–4): 222–77.



Experimenting on Porlieria in damp and dry earth.

Hermann Müller has been ridiculed for teaching children "in the beginning was Carbon".

Will ask about Ernst Krause.

Letter details

Letter no.
Francis Darwin
Charles Robert Darwin
Sent from
Source of text
DAR 209.5: 230–2
Physical description
ALS 2pp †, CD note, encl 2pp

Please cite as

Darwin Correspondence Project, “Letter no. 12075,” accessed on 23 May 2024,