Gerniinatiun 0/ Streptocarpus caulfscens. 363 



one of these is observed to become larger, the other re- 

 maining stationary. Tlie larger cotyledun goes on growing, 

 develops a distinct petiole, and ultimately forms a leaf 

 differing in no essential respect from the foliage-leaves 

 succeeding it on the stem of this caulescent species. A 

 further peculiarity is that the cotyledons thus unequally 

 developed, though at first oppositf^ each other, become, as 

 growth proceeds, separated by an internode, the larger 

 cotyledon being carried up uearly half an inch higher than 

 the smaller one — a very remarkable phenomenon in a 

 dicotyledonous plant. The larger cotyledon, moreover, is 

 evidently of no greater persistence than the foliage-leaves 

 wdiich succeed it, and which, as already said, it closely 

 resembles ; and in this it differs remarkably from the other 

 species mentioned, where the large cotyledon is persistent. 

 As regards the subsequent development of an internode 

 between the unequally developed cotyledons, the late Pro- 

 fessor Dickie {Journal Linn. Soc. Bot., 1867, p. 126) notes 

 t\i-dt in St7'eptocarpiis Rexii and S. primuloides "the two 

 cotyledons are at first opposite and equal in size. After 

 some time, however, they become alternate, the space 

 between the two varying somewhat in difi'erent seedlings. 

 At a more advanced stage, the upper cotyledon thus 

 separated from its fellow begins to enlarge, the other 

 retaining its original size and afterwards decaying." It is 

 interesting to note that in Streptocaijms caulesccns, also, it 

 is the upper of the two separated cotyledons which becomes 

 enlarged. In the axils of both of the cotyledons buds are 

 developed ; in that of the larger cotyledon, in the first place, 

 a primary axillary bud, and then a little later an accessory 

 one placed vertically below the primary bud, betw^een it 

 and the base of the cotyledon. It might be a question for 

 evolutionists whether to regard the condition of S. caul- 

 esccns as a step towards the highly differentiated one of >S'. 

 jjolyanthus, or as a step towards reversion to a more normal 

 development ; a speculation, perhaps, scarcely worth enter- 

 ing upon. 



Explanation of Plate XIV. 

 Seedling Plant of Sfrepiocarpus caulesceiis. 

 X = Cotyledon which remains stationary in development. 



