PLANT ORGANS AND ORGANISMS IQ5 



Triangular, as in the (Enotheras. 



Echinate, as in the Malvacea. 



Spherical, as in Geranium, Cinnamon and Sassafras. 



Lens-shaped, as in the Lily. 



Spinose, as in the Composite. 



Barrel-shaped, as in Polygala. 



Under the microscope the immature pollen grain generally consists 

 of two membranes, an outer firmer one called the exospore, which 

 may be variously marked and which possesses deficiencies in the 

 form of "pores" or "clefts," and an inner delicate cellulose mem- 

 brane called the endospore, which surrounds a protoplasmic interior 

 in which are imbedded a nucleus, oil droplets and frequently starch 

 or protein. 



Pollinia. These are agglutinated pollen masses which are com- 

 mon to the Orchidacea and Asclepiadacece. 



The pollen of many plants, notably certain species of Composite, 

 Graminece and Rosacea, has been shown to be responsible for "Hay 

 Fever." At the present time serums, extracts and vaccines are 

 manufactured from pollen to be used in the treatment of this disease. 



The Gyncecium or Pistil System. This is the female system of 

 organs of flowering plants. It may consist of one or more modified 

 leaves called carpels. Each carpel or megasporophyll is a female 

 organ of reproduction. In the Spruce, Pine, etc., it consists of an 

 open leaf or scale which bears but does not enclose the ovules. In 

 angiosperms it forms a closed sac which envelops and protects the 

 ovules, and when complete is composed of three parts, the ovary or 

 hollow portion at the base enclosing the ovules or rudimentary seeds, 

 the stigma or japical portion which receives the pollen grains, and 

 the style, or connective which unites these two. The last is non- 

 essential and when wanting the stigma is called sessile. The carpel 

 clearly shows its relations to the leaf, though greatly changed in 

 form. The lower portion of a leaf, when folded lengthwise with the 

 margins incurved, represents the ovary; the infolded surface upon 

 which the ovules are borne is the placenta, a prolongation of the 

 tip of the leaf, the stigma, and the narrow intermediate portion, the 

 style. A leaf thus transformed into an ovule-bearing organ is called 

 a carpel. The carpels of the Columbine and Pea are made up of 



