'9°9l 



BARBER-FRUITS AND SEEDS OF CUCURBIT ACEAE 2 7 i 



forated plates in some tubes and have not found them in those con- 

 taining granular milky contents which harden in alcohol, therefore 

 hall mention both in the following descriptions. These element 

 occur in considerable numbers throughout the middle ti>sues of the 



pericarp. 



Each seed has a firm spermoderm of many layers, a thin collapsed 

 perisperm and endosperm, and a large embryo consisting of two large, 

 flat, leaf-like cotyledons and a small radicle. 



Spkrmoderm.— Authors variously state the number of layers in 

 this leathery coat or shell as four 17 to ten. 21 I myself con>ider it as 

 consisting of five distinct tissue layers, the second being occasionally 

 differentiated into two, and the fourth often into two or three forms 

 of cells arranged in as many layers. It is developed from the two 

 integuments (fig. 10), the outer integument forming the three outer 

 and part of the fourth layers, the remainder of the coat developing 

 from the inner integument. 



i. The epidermis consists of a single layer of prismatic palisade 

 cells, polygonal in surface view. They are usually of equal height 

 over the flat surface of the seed, increasing in height at or on both sides 

 of the edge. The radial walls of a few species (as Echinocystis lobata) 

 are uniformly thickened ; in all the other seeds they have either straight 

 or branched thickenings running from the inner to the outer tangential 

 •alls. The outer walls, and frequently the inner, are thickened. 



Vogl, 8 the only author that notes the presence of starch m this 

 la yer, gives no description of the grains. According to my own 

 observation they are small, globular, reaching a maximum diameter 

 of 7 M. the larger ones showing a central hilum but no rings. hex 

 Polarize very indistinctly. 



cells 

 cells 



piderm 



ichymati/'.cd 

 lavcr. The 



long 



e either small, pitted, without intercellular spaces (Cucurmia;, 

 Jtudinally elongated, arranged end to end in rows, with numer- 

 0U * characteristic intercellular spaces (Cucumis), or form a tnu 

 ^ of greatly thickened irregularly arranged cells. No contend 



ar c evident. 



v Sderenchyma.-Thh consists of a layer of exceedingly thick- 



21 Exglkr und Prantl, Pflanzcnfarnilieti IV. 5- 8 - 



