202 M. A Chrysler. 
of the species examined both wounded and healthy specimens were 
available. Outside the genus Pinus, wounded and perfect specimens 
alike showed no tyloses. Within this genus, wounded roots appeared 
to have the tyloses somewhat better developed than did perfect roots. 
In order to investigate further the effect of wounding, two 
series of experiments were made. In the first of these, stout 
galvanized iron wire was tightly bound in the form of a ligature 
around roots of the following species : Pinus strobus, P. austriacci. 
P. resinosa, Picea excelsa, Larix occideutalis, Abies subalpina. These 
trees were growing in the Harvard Botanic Garden. After 
remaining ligatured for two months (June to August, 1907), the 
% 
sections of the various roots were removed from the trees, preserved 
and later examined. In the case of P. strobus the last annual ring 
showed only slight inflations of the medullary ray cells. It will be 
recalled that the heart wood of this species ordinarily does not 
show well-developed tyloses. Sections of P. ciustriaca and resinosa 
showed £L few unquestionable tyloses in the last annual ring ; these 
roots were too young to have heart wood. The roots of Picea and 
Larix showed areas of distorted elements, including both parenchyma 
and tracheids, but no tyloses, while Abies responded to the treatment 
by the usual production 1 of a large number of traumatic resin ducts, 
but no appearance of tyloses. 
The second series of experiments consisted in cutting off 
branches and setting the cut ends in vessels containing water. The 
species thus treated were Pinus strobus, P.flexilis, P. austriacci, P. 
resinosa, P. silvestris, Larix occidentalis. The branches were left 
with the cut ends in water for two months, then preserved and 
examined. In no case were any tyloses observed. It was long ago 
observed by Unger 3 that shoots of Canna treated thus showed an 
abundant development of tyloses near the cut end, and upon these 
grounds he concluded that tyloses are produced as the result of 
wounding. 
These experiments acquire additional interest when considered 
in connection with recent observations by Jeffrey. This author 
shows that resin canals are produced as the result of wounding in 
genera in which they are normally absent, e.g., Abies (l.c.) and 
1 See Jeffrey, E. C. The Comparative Anatomy and Phylogeny 
of the Coniferales, Part 2. The Abietineae. Mem. Boston Soc. 
of Nat. Hist. 6; I., pp. 1—37. Pis. 1—7, 1905. 
* Unger. Ueberd. Ausfiillungalternderu. verletzter Spiralgefasse 
durch Zellgewebe. Sifzungsber. d. Wiener Acad. 56, 1867. 
