362 Professor Dickson on the 



up ill surgery, his favourite branch of study, he often 

 diver<jc(l during his travels to natural history pursuits, 

 and made collections of plants, &c., which would have done 

 credit to one with more pretensions to a knowledge of the 

 subject than he professed to have. 



On the Gerininatio7i of Streptocarpus caulescens. 

 By Professor Dickson. (Plate XIV.) 



(Read 11th May 1882.) 



My observations on this plant have been made on speci- 

 mens raised in the Botanic Garden, from seeds recently sent 

 home by Mr John Buchanan, from Blantyre, Central Africa. 



It is already known tliat in the germination of such 

 species as St7xptocarpus Bexii and S. polyanthus, from 

 South Africa, the two cotyledons are at first very small 

 and of equal size, but that while one of these remains 

 stationary in development, and finally disappears, the other 

 continues to grow, forming an elongated sessile leaf of 

 considerable size, lying flat along the surface of the ground. 

 In tliese species the enlarged cotyledon persists tliroughout 

 the life of the plant, and is the only leaf-organ performing 

 proper leaf-functions, the other leaves being developed 

 merely as bracts in connection with the inflorescence. A 

 similar development, it can hardly be doubted, occurs in 

 Accmthonema strigosum (described by Sir J. D. Hooker in 

 the Botanical Magazine, vol. xxxviii. tab. 5339), a plant 

 belonging to the same natural order {Gesne7riccce) , and also 

 a native of South Africa. It is noteworthy that in yet an- 

 other South African plant, though of very different affinities, 

 — the celebrated Weliuitschia, — we have also an instance of 

 leaves, either the cotyledons, or, as would appear from Mr 

 Bower's researches, the two first leaves of the plumule, 

 becoming much enlarged, persisting throughout the life- 

 time of the plant, and performing exclusively, in absence 

 of any other foliage-leaves, the ordinary leaf-function, just 

 like the enlarged cotyledon of Streptocarpus polyanthus. 

 In the Blantyre Streptocarpus the plant germinates at first 

 with two minute cotyledons of equal size and opposite to 

 each other, i.e., at the same level. A little later, however. 



