140 LABORATORY STUDIES OF THE FRUIT 



of which would have a cliauce ol germinating upon Ihu plot of ground 

 occupied by the parent, unless carried elsewhere. Take as au example 

 the Cranberry, studied in Exercise XXXV. Allow lil'ty berries to a 

 siii'de bush, and multiply by the number of seeds actually observed 

 ill one berry. The resulting product represents the possible number 

 of seedlings upon less than a S(piare yard of ground. 



That even one seedling should occupy part of the soil held by the 

 p)arent plant would evidently be disadvantageous to both. Accord- 

 ingiv, plants exhibit a great variety' of devices by which the service 

 of various agencies is secured for the dispersal of the seeds. The 

 means of dissemination maybe (1) some feature of the coat of the 

 seed itself, ('2) some special character, construction, or outgrowth of 

 the pericarp. The tirst case has been seen in the Milkweed ; the 

 second remains to be studied in more detail. 



Bladder Nut. — Examine the bladdery fruit before dehiscence, not- 

 ing (1) the morphology of the pericarp, (2) the number of carpels, 

 ami (•!) the relative size of the pericarp and the seeds. Place the 

 fruit on the table. Blow it about. The object of the inflated peri- 

 carp becomes ;ipparent. 



J)ra\v the fruit, natural size. Indicate in dotted line the position 

 and size of the seed. 



Curled Dock. — ^Vith a lens examine the tliree-winged and coarsely 

 veined pai'ts, each bearing at its base a granule i-esembling a seed. 

 They are persistent sepals, and are closely appressed. Hidden between 

 them is the three-angled lu-liiiiii (dry pericarp, containing a single 

 seed). 'J"he dispersal apparatus here comes from the calyx. Xote 

 hiiw readily tlie fruit is driven by a mere lireath. 



Draw the fruit, with one sepal removed to show acliene, magnified 

 ab(.)ut eight diameters. 



Bur Marigold. — The Ijarbcd bristles, well seen with the lens, are 

 morphologically the border of the calyx, the lower part of which is 

 adherent to the pericarp. AVhat is the mode of dissemination? 



Dra\\' the fruit, magnified about four diameters. 



Witch-hazel. — Xotice : — 



(1) The pericarp proper, with the old calyx surrounding the lower 

 half. (•_') The partial splitting at the tips of uno[iened fruits, (o) The 

 number of cells (hiciili) in the opened capsules. (4) The mode of 

 dehiscence. The Inruli are split open along the median line in each 

 case. Tins is /or»/(cfV/n/ dehiscence. (-5) The backward curving of the 

 open jaws, (fi) The very hard, smooth inner surface of the locxli, and 

 the similar surface of the seeds, which indeed makes it rather difficult 

 to htild them securely between finger and thumb. (7) Cut away the 

 calyx and the outer, softer layer of the pericarp. It will lie seen that 

 the inner .nnd immediate receptacle of the .seeds is a bony and rather 

 thick-walled double case. There was originallv one seed in each 



