206 STUDY OF COMMON PLANTS. 



It will be seen that all three kinds have a relatively 

 thick pericarp and abundant, white endosperm, within which 

 lies the small embryo, near the apex of the fruit, and con- 

 sequently not seen in sections taken lower down. In the 

 pericarp are a number of vittae, or oil-tubes. The corian- 

 der has two of these in each mericarp lying next to its in- 

 ner, or ventral face. In fennel and dill, in addition to 

 these two, there are four more vittse alternating with the 

 ribs of the outer, or dorsal face. 



Draw in outline, representing accurately the position of 

 ribs and vittse. Letters and guiding lines will conduce to 

 clearness. 



IV. Write a complete description of the three fruits, 

 taking care to distinguish the characters common to all, 

 from those that are only of specific or generic value. 



RELATIONSHIP. 



Later in the season many other species of umbellifers 

 that will serve for comparative study are easily obtained. 

 Thaspium, or some other common genus, may be substi- 

 tuted for Erigenia if found more convenient. As the 

 study is continued it will be apparent that the external 

 characters to which attention has already been directed, 

 although variously modified, are constantly repeated in 

 nearly all the genera. The hollow stem, compound leaves 

 with inflated petioles, flowers in umbels, and the very 

 marked and distinctive features of flowers and fruit occur 

 over and over again, sometimes in connection with specific 

 characters by which a given plant is easily identified, some- 

 times with these characters so far wanting that identifica- 

 tion becomes extremely difficult. All in all, the family is 

 one of the best marked groups in the vegetable kingdom. 

 It includes about thirteen hundred species, distributed 



