938 REV. G. HENSLOW ON THE ORIGIN OF PLANT-STRUCTURES 
M. Aug. Pyr. de Candolle came to the same conclusion in 1827 ; 
for he thus wrote about Rhus Cotinus :—‘ Peut-étre la sve 
destinée & nourir les fruits ne trouvant plus d’emploi, lorsque 
ceux-ci ont avorté, produit-elle ce développement extraordinaire 
de poils. Quelques filets d’étamines (Verbascum, Tradescantia) 
deviennent aussi poilus quand les anth¢res avortent, et pro- 
bablement par la méme cause’”’*, 
Dr. M. T. Masters observes, when speaking of the hair on the 
barren pedicels of Rhus Cotinus, or the “ Wig-plant,” as it is 
called :—“A similar production of hair may be noticed in many 
cases where the development of a branch or of a flower is arrested ; 
and this occurs with especial frequency where the arrest in growth 
is due to the puncture of an insect, or to the formation of a 
gall}. 
As an illustration of this last-mentioned fact, it may be 
often noticed how Veronica Chamedrys terminates its shoots 
with an excessively woolly globular bud. A similar thing happens 
to a heath, Hrica scoparia, common on the hills around Cannes. 
In the latter plant the abnormal leaves are broad, ovate, and 
densely hairy ; while the ordinary leaves are linear and glabrous. 
These globular structures in both plants are due to the irritation 
set up by the presence of grubs. The axis and the innermost 
leaves are arrested at the apex, while in compensation the lower 
leaves of the bud alter their character, enlarge and become densely 
elethed with hair f. 
The fact of hairs being developed over and about the fibro- 
vascular cords is of common occurrence, and, under the above 
aspect, becomes very significant in such cases as in desert-grasses, 
Javender, &c. Pfitzer observes, “Almost all grasses inhabiting 
very dry localities have leaves with well-marked longitudinal 
folds” $, the stomata being situated within the grooves, while the 
ridges correspond to the vascular and fibrous cords. The tooth- 
like (or branched, as e. g. on the calyx of Lavender) hairs of the 
grasses project like chevaua-de-frise over the grooves. They 
have swollen bases capable of imbibing moisture; and so in all 
* ‘Organographie Végétale,’ tom, i. pp. 111, 112. 
t ‘Teratology,’ p. 472. 
+ I have elsewhere called attention to this fact in its analogy with the 
results of the irritating action of the pollen-tube. See ‘Origin of Floral Struc- 
tures,’ p. 164 seqg. 
§ Quoted by De Bary, Comp. Anat. &e. p. 50. 
