THE ALUMNI JOURNAL. 



175 



filled with resin, and from these radiate 

 the immediately adjoining parenchymatic 

 cells. The epiearp shows a distinct line 

 of demarcation from the mesocarp. 



The Mesocarp — The parenchyma pre- 

 sents several different lorms of cell in 

 not clearly defined layers . The outer 

 layer is of loose tangentially elongated 

 cells connecting mesocarp and epiearp . 

 The second layer is of oblong cells, irre- 

 gularly strung together, containing two 

 kinds of oil, which is either collected along 

 the cell-wall or scattered promiscously 

 about. Oneoil is of very light yellow color, 

 forming regular globules about .0108 

 mm. in diameter, the other, a darker oil, 

 is in irregularly shaped drops, measuring 

 from .0081 mm. to .0405 mm. in diameter. 

 Half way through the mesocarp the cells 

 become nearly equilaterial. The inner 

 fourth of mesocarp forms a layer of uni- 

 form thickness around theputamen. The 

 outer portion of this consists of elongated 

 somewhat thick-walled, very little pitted 

 cells, crowded and irregularly compressed 

 together. These contain oil globules. 

 Then comes a single row of square or 

 oblong narrow cells, polygonal or longi- 

 tudinal section, containing calcium oxa- 

 late crystals. This layer is sometimes 

 wanting. Between this and the putamen 

 is a layer of about three cells deep of 

 irregularly triangular empty cells attach- 

 ing mesocarp to endocarp. In the last 

 layer are no fibro-vascular bundles nor 

 resin- cells. In the pulp are many large 

 oval cells about .0625 mm. x .162 mm. 

 occurring singly or in twos or threes, or 

 five or six forming a segment of a circle. 

 They are filled with a dark-brown resin, 

 and to the naked eye show as brown 

 streaks through the pulp. 



The fibro-vascular bundles are of the 

 closed collateral type, the xylem being 

 always towards the centre of the fruit. 

 They are numerous and irregularly scat- 

 tered. 



The Xylem is composed of several large 

 vessels, partially encircled by thinner- 

 walled wood-cells, on longitudinal sec- 

 tion exhibiting several spiral ducts sur- 

 rounded by narrow somewhat pitted ducts 

 and outside of all, cells with cratei-form 

 openings in the walls. 



The Philoem portion consists of soft 

 bast and sieve-tissue, no hard bast being 

 distinguishable. In longitudinal section 

 the cells are much elongated, with trans- 

 verse septa. Each bundle is surrounded 

 by collenchymatous cells which, becom- 

 ing larger from within outward, grade 

 into the general parenchymatous tissue. 

 This collenchyma contains numerous 

 globules of a light-colored oil, which on 

 longitudinal section are seen to form a 

 tube-like series running through the col- 

 lenchyma. Diameter of a bundle = 0.5 

 mm, to 0.1 mm. Diameter of a duct = 

 .0054 mm. to .0270 mm., cavity % of 

 total diameter. Thickness of collenchyma 

 tissue on each side of bundle, .0375 mm. 



The Endocarp consists of much pitted 

 schlerenchyma cells, which have a diam- 

 eter of about .0425 mm. and are mostly 

 isodiametric though a few are two or 

 three times as long as broad. The cavity 

 is about yi the total diameter of the cell. 

 The inner surface of putamen shows cells 

 somewhat elongated and of very loose 

 structure, linked together in many in- 

 stances by large, comparatively thin- 

 walled, little-pitted, more or less quad- 

 rangular cells. The extr^ne outer layer 

 shows very small isodiametric stone-cells, 

 making a distinct line of demarcation be- 

 tween endocarp and mesocarp. Between 

 the endocarp and the seed is a small space 

 filled with a sticky, viscous substance 

 having a very sweet oily taste. It con- 

 sists mainly of glucose, with some oil. 

 This sticky substance has disappeared 

 from many of the dried fruits. 



The Seed. — Thp testa is coyaiposed of 

 several kinds of cells : externally « 



