SPERMATOPHYTES— ANGIOSPERMS 355 



der of appearance of floral parts is (1) calyx, (2) stamens, (3) carpels, 

 and (4) petals. The ovary is compound (syncarpous). 



With its 6 stamens (2 of them shorter than the other 4), 2 carpels, 

 and 4 nectaries marking the place of the missing parts, Capsella shows 

 an interesting transition from the pentacyclic to the tetracyclic type 

 of flower. Transverse sections of single flowers, just before the small 

 petals expand, are best for this study. 



Ranunculus, which is also hypogynous, will illustrate the develop- 

 ment of the simple (apocarpous) ovary. The ovules appear quite 

 early, so that the archesporial cell, or even the megaspores, may be 



Sepal 



Microsporophyf/ 

 ^ (Stamen) 



■Wiegasporophyl! 

 (Carpel) 



'-Petal 



'Microsporophyll 

 (Stamen) 



Fig. 124. — Capsella bursa-pastoris: floral development. X85. From Chamberlain's Elements 

 of Plant Science (McGraw-Hill Book Co., New York). 



seen while the carpel is still as open as in any gymnosperm. The whole 

 structure is a simple strobilus (Fig. 125). 



Rumex crispus (yellow dock) is also a good hypogynous type, and 

 the densely clustered flowers afford a fine series of stages. Besides, in 

 transverse sections, the early stages in spermatogenesis are very clear. 



In the willows, Salix, the bud scales must be removed and the copi- 

 ous hairs should be trimmed off as much as possible with scissors, 

 after which the catkin should be slabbed a little on opposite sides to 

 facilitate penetration. This is a fine illustration of a compound stro- 

 bilus. 



The cat-tail, Typha, presents a simple type of floral development. 

 The leaves should be dissected away long before the flowers can be 

 seen from the outside. The cylindrical clusters, varying in diameter 

 from 2 or 3 mm. up to the size of one's finger, will afford a complete 

 series of stages. Until the spike reaches the diameter of a lead pencil, 



