On the Haustoria of Pedicularis vulgaris, Tournef. 
BY 
A. C. MAYBROOK. 
With five Figures in the Text. 
Introduction. 
S O far as it has been possible to ascertain, the only account of the 
haustoria of Pedicularis is due to Leclerc du Sablon, 1 who described, in 
1887, the development and structure of these organs in Pedictdaris sylvatica . 
The writer does not mention the existence of ‘ phloeotracheides * in the 
haustoria ; indeed the conception of phloeotracheides in root haustoria did not 
arise till much later (1910), when Benson 2 demonstrated their presence in 
Exocarpus , and put forward the suggestion that they existed in all root 
parasites. 3 The following piece of work was undertaken with the object of 
ascertaining whether such elements existed in the haustoria of Pedictdaris , 
and the results may therefore be of use in supplementing those of 
du Sablon. 
Methods. 
The material was fixed in acid alcohol, and was subsequently preserved 
in 70 per cent, alcohol. Microtome sections were used ; the most satisfactory 
double stain for these was found to be cotton red and aniline blue. 4 Stains 
of suitable strength were found by adding 100 c.c. of 80 per cent, alcohol to 
\ grm. cotton red, and 1,000 c.c. of 80 per cent, alcohol to 2 grm. aniline blue 
and 1 c.c. picric acid. The sections were placed for twenty-four hours in 
cotton red, washed with 80 per cent, alcohol, and then placed in aniline blue 
1 Leclerc du Sablon : Recherches sur les organes d’ absorption des plantes parasites (Rhinanthees 
et Santalac^es). Ann. des Sc. Nat. Bot., 7 e ser., 1887. 
2 Benson, Margaret : Root Parasitism in Exocarpzis (with Comparative Notes on the Haustoria 
of Thesium). Ann. Bot., vol. xxiv, 1910, p. 671. 
3 Benson (1. c.) describes phloeotracheides as lignified cells which are lined with protoplasm 
but contain no nuclei. Their end walls are absorbed as in open tracheides. Embedded in the matrix 
lining the walls are a number of granules which probably consist of hydrolysed cellulose which has 
been deposited as amylodextrin. Their function is to collect and act as a pathway for the hydrolysed 
products of solution of the host cells. In the case of Exocarpus, which is subject to drought 
conditions combined with much isolation, these elements are supposed to act as a filter, since, by the 
precipitation of the granules, the ascending sap is less charged with dissolved carbohydrate. 
4 The instructions for the use of this combination were kindly given me by Miss Bancroft. 
[Annals of Botany, Vol. XXXI. Nos. CXXIII and CXXIV. July and October, 1917.] 
