190 PROCEEDINGS OF THE ACADEMY OF [1897. 



cells, varying as it does in almost all plants, each species having its 

 own peculiar method of developing cork cells, fully accounts for the 

 red color of the annual growths in Cornus stolonijera. 



FOLIAL ORIGIN OF CAULINE STRUCTURES. 



The endeavor to conceive axial and foliar organs as morpholog- 

 ically distinct, leads to difficulties easily surmounted by the concep- 

 tion that every part of a plant is but modified leaf-blade. In striv- 

 ing to regard stem and leaf as essentially distinct entities, we become 

 wholly lost in studying the genesis of the tendril, and we are com- 

 pelled to say of them they " may be axial or they may not. This 

 may ordinarily be determined by position. Any direct continua- 

 tion of stem or branch must be of an axial nature, that is, of the na- 

 ture of stem ; and the same is true of whatever primarily develops 

 in the axis of a leaf. Conversely, whatever subtends a lateral axis 

 or branch may be taken for a leaf or foliar production being in the 

 place of such." 3 But the difficulty of carrying this idea along to a 

 consistent conclusion becomes apparent at p. 118 of the work cited, 

 where the tendrils of Cucurbitacese are pronounced " peculiar and 

 ambiguous, on account of their lateral and extra-axillary position 

 and the manner in which the compound ones develop their 

 branches." 



That a leaf and stem must be morphologically the same seems 

 proven by the well-known fact that leaves often develop into stems. 

 The author has seen buds at the ends of the leaves of the Japan 

 Umbrella Pine, Sciadopitys, and a large number of species of plants 

 are raised by florists from leaves of which Begonia is a familiar 

 example. The section of an articulated stem of Opuntia is tech- 

 nically stem ; yet the flower which, morphologically stated, is but a 

 " bundle of leaves," often shows that it is simply a whole section 

 metamorphosed. We call the deciduous portions of Taxodium dis- 

 tichum " leafy branchlets " simply because the least vigorous ones 

 perish. If all were to fall, they would be regarded as pinnate 

 leaves, and it is barely necessary to refer to the fact that numerous 

 plants bear flowers on the leaves, as a tree of the Jujube, Ziziphus 

 vulgaris, before the author as he writes, amply illustrates. 



By adopting the hypothesis that a tendril is always cauline, we 

 shall have to admit that stem is of folial origin in a study of Big- 

 noniaceous plants. A number of species have trifoliate leaves when 



3 Gray's Structural Botany, 1879, p. 54. 



