i92o] DUPLER—TAXUS CANADENSIS , 509 



after fertilization, and by. seed maturity has reached the base of 

 the seed. In the meantime the aril has developed, surrounding 

 the hard nut like seed. 



Aril. — In the young ovule there is no indication of the aril, 

 but about the time of pollination the aril primordium begins to 

 develop as a ring at the base of the ovule (fig. 40). Its early 

 development is contemporaneous with the chalazal growth of the 

 ovule. In its early stages it is a flat saucer-shaped structure 

 (% s - 5> J1 ) of greenish color and of slow growth until the seed is 

 nearly matured and the seed coat hardened. Then there is very 

 rapid growth; it soon becomes cup-shaped and reaches its mature 

 condition, that of a large red fleshy cup inclosing the hard seed 

 (figs. 8, 43). The chalazal portion is a tissue of small cells, traversed 

 by the vascular elements which supply the hard integument. The 

 sides of the aril consist of Very large delicate-walled cells, filled 

 with a watery material, the long cells being extended radially and 

 obliquely upward. The epidermis is a narrow layer of small pig- 

 mented cells, and contains fairly numerous stomata, oriented 

 longitudinally. 



The morphological nature of the aril has been one of the mooted 

 questions in the taxads, having been regarded as: (1) a special 

 outgrowth surrounding the ovule, (2) a carpel, (3) representing the 

 ovuliferous scale of other forms, (4) a second (outer) integument, 

 and (5) the fleshy layer of a single integument. Richard (25) 

 regarded the aril as the equivalent of the collar of Ginkgo, an 

 accessory structure formed from the flower stalk. Blume (4) 

 thought of it as a carpel, and Baillon (2) as an expansion of the 

 axis surrounding the ovary. Parlatore (22) seems to have been 

 the first to regard the aril as the morphological equivalent of the 

 ovuliferous scale of other forms, a view followed by Celakovsky (8) 

 and Worsdell (39), both claiming the ovuliferous scale of conifers 

 to be the morphological equivalent of the "epimatium" of the 

 podocarps, of the outer fleshy layer of the ovule of Torreya and 

 Cephalotaxus, and of the aril of Tax us. Sixnott (33), in his study 

 of the podocarps, holds a similar view with reference to Cephalo- 

 taxus, the logic of which would be to regard the aril of Taxus in the 

 same light. Strasburger (35), with Baillox (2), regarded the aril 



