214 COMPENDIUM OF GENERAL BOTANY 



A. CALYX, COROLLA, NECTARIES. THE FLOWER AS A WHOLE. 



In Picea excelsa the ovules are protected by the overlapping 

 of the cone- scales. We have learned that the torus with the style 

 and stigma is not necessary in this case. Because of the firmness 

 and arrangement of these scales no calyx is necessary (among $ 

 flowers bud- scales protect the stamens). Since fertilization is 

 brought about by the wind, a colored corolla is also unnecessary 

 the color serves to attract insects ; the nectaries are likewise absent, 

 their function being to attract insects. Petals are also absent from 

 number 2. In numbers 3 and 4 they are present, because hya- 

 cinths and cherry-flowers, as well as thousands of other colored 

 flowers, are dependent upon insects for pollination. The con- 

 ditions of reproduction in spite of hermaphroditism (in 2, 3, and 4) 

 are so regulated that the great majority of hermaphroditic or bi- 

 sexual flowers are dependent upon cross-fertilization. In only a 

 very small number of cases has it been found that self -fertilization 

 is more beneficial. 



The pine (1) is dioecious. Since the wind is the means 

 by which pollination is brought about (anemophilous), it is evident 

 that pollen must be very plentiful to insure 

 fertilization ; this we find to be the case. 

 Sometimes pollen-grains possess vesicular en- 

 largements of the exine which facilitate their 

 distribution by the wind (Fig. 134, bl). 



In the anemophilous Graminece (2) the 

 FIG. 134.-Pollen grain 

 of Pinus Pinaster. pollen-grams are caught and retained by the 



(After Sachs.) delicate bristles of the stigma (see Fig. 135). 



The small scales at the base of the stamens, the so-called ' ' lodic- 

 ulse, ' ' have a mechanical function ; by swelling they assist in open- 

 ing the flower. At least they need not be considered as forming a 

 ' ' rudimentary ' ' perianth or calyx, since the bracts or glumes 

 take the place of the calyx. As a rule, each individual flo\ver has 

 two secondary bracts (palece) and each spikelet has two primary 

 bracts (glumes). It would be wholly wrong to suppose that the 

 flower of the conifers or grasses is rudimentary or imperfect as 

 compared with the flower of the cherry-tree. 



Numbers 3 and 4 represent types of flowers whose pollen 



