Obituary. — Henry Harold Welch Pearson . xv 
of its relationship to the floras of neighbouring regions. One ot his aims 
in visiting the Karasberg range, which rises from the level plateau of the 
Kalahari desert, was to search for clues to the past history of the South 
African flora. He always arranged his routes according to a well-considered 
plan of attack upon the phytogeographical questions suggested by the 
different types of vegetation and the varied physical conditions of the 
countries through which he travelled. Had Pearson lived a few years 
longer there is no doubt he would have worked up his field-notes into 
a connected whole, and knowing how well qualified he was by training and 
by his ability to see things in their true perspective, one is able to realize 
to some extent how valuable such a digest of his knowledge and mature 
experience would have been. 
His thorough treatment of the problems presented by the root- 
parasite Striga lutea, a Scrophulariaceous plant locally known as the 
Rooibloem or Witchweed, which causes serious loss to cultivators of Maize, 
and the valuable practical directions for dealing with the disease afford 
further evidence of his versatility and of his desire to demonstrate the 
importance of Botany as an applied science. With the assistance of Miss 
Stephens, one of his pupils, he studied the details of the haustorial structures 
and their connexion with the host ; he also investigated the germination 
and dispersal of the small seeds and made many experimental trials of 
different methods of dealing with the pest. Previous attempts to germinate 
the seeds of Striga had been unsuccessful and Pearson proved that 
germination occurs only in presence of the host. 
During a halt in Namaqualand Pearson made observations on the 
internal temperature of Euphorbia virosa and Aloe dichotoma . He found 
that Euphorbia , with its large chambered pith, responds more quickly than 
the Aloe to changes in the external temperature and attains higher maxima. 
He also investigated the effects of wounding : in Aloe the lowering of the 
internal temperature is due to evaporation at the surface of water conducted 
through the xylem, while in Euphorbia the lowering is due in part to 
surface evaporation, but also to the expansion of gases imprisoned in 
the pith. 
In answer to a request for a few words about our friend the High Commis- 
sioner in London for British South Africa, the Right Hon. W. P. Schreiner, 
wrote as follows : ‘ I don’t think that I can really add anything that is 
not better said by others about dear Pearson. I entirely associate myself 
with what is written of him in prose and poetry in an article in the “ South 
African College Magazine” for November, 19 16, where he is placed at the 
front of the Roll of Honour. My abiding impression of him is of a shining 
bright personality. His laugh was a tonic. He was the most cheery man 
at cheerful gatherings such as our remote Oxford and Cambridge dinners 
on Boat-race night, or at the annual College feasts at Cape Town. But 
