34 COLLEGE BOTANY 



The tuber type (Fig. 18), which is a short, fleshy underground 

 stem, as the potato. This type serves for storage of reserve food 

 materials. (10) The bulb type (Fig. 19 ), which is a very short 

 stem with fleshy leaves and is usually produced underground. 

 It is characteristic of onions, tulips, hyacinths and many other 

 plants. This type also serves for storage of food materials. 



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FIG. 11. Excurreric type of stem 



(11) The submerged type or stems of plants that grow under 

 water. Since they float in the water, the fibrous tissue is usually 

 very poorly developed and the intercellular spaces very large. 



(12) The large thorns (Fig. 34) on the horny locust are 

 modified stems, 



Bulbs (Fig. 19) are specialized stems in which the inter- 

 nodes are very short and the leaves modified into thick, overlap- 

 ping, scale-like structures. In the onion, lily, tulip and hyacinth 



