6 STUDIES IN ROOT-PARASITISM. 
were not tried in growing seedlings in garden earth from the 
commencement, but those grown in sand were chiefly intended to 
supply material for the study of the young stages of the hausto- 
rium, in which respect the results were disappointing. 
The difference from Santalum album in the development of 
root-hairs is not confined to the young plants, for in old roots in 
nature the parts immediately behind the broad white ends were 
found to be covered with a felt-work of delicate hairs, in striking 
contrast to the smooth white rootlets in sandal (Plate IT, fig. 3). 
On the other hand, the copious development of haustoria on the 
young roots grown in sand, so striking a character in Santalum, 
was much less evident in Olax. A few haustoria were found, but 
they were widely scattered, few self-attachments were met with 
and not nearly so many cases of adhesion to pebbles or grains 
of sand (Plate II, fig. 4). 
The free development of unattached haustoria in Santalum 
was regarded by Scott as indicating waning parasitism. This 
character must be extended to Thestzwm where many haustoria are 
unattached in the young roots, as has been pointed out by Leclere 
du Sablon and others and observed by myself in Indian species. 
In both of these genera the root-system, as such, is poorly 
developed and root-hairs are more or less absent. These facts 
appear to indicate not so much a waning parasitism asa very well- 
developed one. In Olaa on the other hand, the comparative 
rarity of haustoria in the earlier stages of growth, the well- 
developed root-system and the abundant root-hairs even in old 
plants, suggest rather incipient parasitism. According te Hein- 
richer,’ in plants becoming parasitic, haustoria are probably first 
developed, and then reduction of the root-system takes place. 
The parasitism of Olax scandens thus appears to be in a com- 
paratively elementary stage, judging by the absence of the 
multitudes of unattached haustoria in the seedlings, the well- 
developed root-system and the abundance of root-hairs in both 
| E Heinricher, Die griinen Halb-Schmarotzer, Il Huphrasia, Alectorolophus and Odon- 
tites. Jahrb. f. wiss. Bot. XXXII, 1898. 
