245 
The dependence on favourable conditions as to temperature ami 
other factors, inlliu'iiohiijr the germination and power nl' infection 
of conidia present in the soil ; also tin- dependence on weather of 
the relative growth of mycelium in an infected tuber, s<-rve t<> 
explain why the disease is much more prevalent during some 
seasons than others, also why during certain seasons there is 
practically no disease present. 
Experiments prove that tubers can only l.e infected during the 
earliest stage of growth ; when the tuber has reached the size of a 
marble and a definite periderm or skin is formed, it is free from 
danger. 
Judged from a morphological standpoint the relationship of 
the fungus causing " leaf -curl" to that of another fungus— 
Mrir;-o.y,<>rii/in to:ii((to, Cooke, parasitic on cultivated tomatoes, 
was some years ago indicated as follows :—" This fundus is closely 
allied to, if not identical with the Mxrms/xn-i mn causing black 
stripe, or blotch on the tomato" ' Tex f -bun/, nf I'/mif-'/isw-s, 
p. 323). Inoculation experiments have proved this supposition i" 
be correct. Conidia produced on a potato plant will miect a 
tomato and V>rr rrr.su. The discovery facilitates matters m lie 
extent of deleting one supposed parasitic entity, and also indicate s 
the danger of the disease passing from one crop to the other when 
the two are growing in close proximity. 
The practical deductions to be derived from the foregoing 
remarks are as follows : — 
Potato tubers for planting should be obtained from a district 
free from disease. 
Potatoes should not be planted, for a period of three years, on 
land that has produced a diseased crop. 
Diseased haulms should be collected and burned or deeply 
buried. This is important, otherwise the land will 
become infected. 
Diseased tomato steins and fruit should be dealt with as 
above, otherwis9 the potato crop may suffer. 
XLI.-DIAGNOSES AFRICANAE: XVIII. 
864. Guarea Thompson!, Sprague et Hutchinson [Meliaceae] : 
ab affini G. Zenkeri, Harms, infiorescentia pyramtdali recedit, 
Arbor ramulis glabris 1 cm. diametro vel ultra. FJni 7-S-juga, 
glabra ; p ■tiolus circa > cm. l«»i gt s. sem t. :■• -. • '- 
inflexis; foliola ohlonga vel oi.ovaio-oblong .i.ranus 
ID -in. m h.n '.. 1 "» 7 ."• i n In*, ip ' obrusa. rdum ivm.-m 
i. mi inata.i onin i n rorusa. 1 si r«.n 
ehartacea. utrinque veiiis et venulis supra inr 
axillares, plures versus apicem ramulorum dispose 
cupularis, 3 mm il. is, 1 mm. diametro, paullo qmnqueunduLitus 
potius quam lobatus, extra pnbescens, intus glaber. Petala 5 
