THE AM ERIC Ay XATi-RALlST. [\()L. XXXVIIl. 



1. The mucilage canals of the Eusporangiate ferns may be 

 regarded as the ancestral forms of the resin passages among the 

 higher plants, but they are obviously the successors of, as they 

 are derived from aggregates of, mucilage sacs as simple, paren- 

 chyma cells. 



2. Resin passages are wholly unknown in the wood of the 

 stem of ferns, the Cycadofilices, the Cycads, Cordaites or 

 Araucarioxylon. 



3. Resin cells are known and are abundant in the pith and 

 bark of Cordaites, but they are absent from its wood. 



4. Resin passages are known in the bark and in the pith of 

 the Cycadacese, of Agathis, Araucaria and of the Coniferales in 

 general. They also occur in the wood of the peduncles of 

 Sequoia and Cycas, and in the xylem of the first year's growth 

 of vigorous shoots in Sequoia and Abies. They likewise occur 

 in the leaves generally. 



5. In Sequoia burgessii from the Eocene, resin passages 

 occur in the medullary rays, but they do not traverse the wood 

 longitudinally, though isolated resin cells do occur there. 



From this it would seem that the fundamental tissue is the 

 most impressionable with respect to the development of these 

 structures, and that after it we have in the same order the 

 peduncle of the inflorescences and the wood of the young 

 shoots, to which latter category would also belong the develop- 

 ment of resin passages in fasciated stems, and such a sequence 

 is precisely what we should expect from our knowledge of the 

 relation which the fundamental tissue bears to other structures. 

 Ac cording to this conception the resin passages may appear in 

 ;ui\ [)ai-i of the woody structure where growth is sufficiently 

 \ l,^'>^ou^, Init such appearance would be temporary and indica- 

 iiw onl\ K)\ a future course of development which has not as yet 

 bccouK' sullu icnlly well impressed upon the organism to form a 

 permaacnl fcatvuv of it. In other words, the tissue exhibits 

 what in other cases would be termed "sports." Such structural 



^M'l'li^-^l to the (lexelopment of tissues no better example is- 

 ;^tt'"^l^:d than that shown l.)y the central strand of mosses, which 

 IS generally accei)ted as prophetic of the future vascular system 



