46 LLOYD. 



specimens, there are found two kinds of leaves. Masters called 

 these two kinds the juvenile and adult forms, anc suggested that 

 the former, which are much the longer and shaiply pointed, 

 represent an ancestral condition. In this way, also, he com- 

 pared Rctinospora to an immature stage of Thuya inasmuch as 

 plants of the former genus suddenly assume the foliage charac- 

 teristics of the latter. It will be seen, however, that these two 

 cases, Piniis and Juniperus are not quite parallel, for the ordi- 

 nary foliage or secondary leaves of the former are produced 

 upon the reduced twigs in groups or fascicles, in which the 

 number of leaves is practically constant for a particular species, 

 while this arrangement is not found in the junipers. The struc- 

 tures in P'uuis which should be compared directly with the leaves 

 of Juniperus are the primary leaves, and later the scales which 

 subtend the fascicles. Dimorphism in the leaves of the seedlings 

 of Piuus is a constant feature. The cotyledons are followed 

 immediately by the primary leaves, so called by Engelmann, ^ 

 and it is only later that the fascicles are produced. The same 

 writer also drew attention to the fact that these primary leaves, 

 or similar ones, are also found upon sprouts of certain species 

 [P. inops, rigida, Canaricnsis^ etc.), and are frequently upon 

 young shoots of Larix. The structure of the cotyledons, pri- 

 mary and secondary leaves were studied comparatively by Da- 

 guillon - in 1890. He included in his studies five genera, Abies, 

 Picea, Pinus, Larix, and Ccdrus, and showed that the ontoge- 

 netic series of leaves from the cotyledons to the adult, present 

 a series of gradations, gradual in Abies, but more pronounced 

 in Pinus. Of the species of Pimis, Daguillon studied four 

 (/^. strobus, pine a, niaritinia and sylvestris). 



The primordial leaves which are produced in the seedling on 

 the stem above the cotyledons are in all cases elliptic in trans- 

 verse section, and have two resin ducts in contact with, or \'ery 

 near the lower epidermis. In P. niaritinia, they are very near 

 the lateral angles. The supporting tissues are less strongly de- 

 veloped and the vascular bundle is single. In one species only 



^Engelmann, "Revision of the genus Finns,'''' Trans. St. L. Acad. IV, i88o. 

 2 " Recherches sur les fuilles des Coniferes." Rev. Gen. d. Bot. II : 154. 1890. 



