SECT. I 



MORPHOLOGY 



19 



Avhile an axillary bud provides for the continuance of the axis of the 

 rhizome. In the flower-producing shoots or inflorescences of Phanero- 

 gams the different systems of branching assume very numerous forms. 

 These will be more fully described in their proper place. 



The Shoot 



The Development of the Shoot. ^ — Under the term shoot a stem 

 and its leaves are collectively included. A stem possesses an apical 

 mode of growth (Fig. 17), and its unprotected growing point is 

 described as naked, in contrast to that of the root with its sheathing 

 root-cap. The apex of the shoot generally terminates in a conical 

 protuberance, called the vegeta- 

 tive CONE. As it is usually too 

 small to be clearly visible to the 

 unaided eye, it is best seen in 

 magnified median longitudinal 

 sections. So long as the apex 

 of the shoot is still internally 

 undifferentiated, it continues in 

 the embryonic condition, and it 

 is from the still embryonal vegeta- 

 tive cone that the leaves take their 

 origin. They first appear in 

 acropetal succession as small, coni- 

 cal protuberances, and attain a 

 larger size the farther removed 

 they are from the apex of the 

 stem. As the leaves usually grow 

 more rapidly than the stem which 

 produces them, they envelop the 

 more rudimentary leaves, and, 

 overarching the vegetative cone, 

 merely undeveloped shoots. 



Fig. 17. — Apex of a shoot ofa phanerogamic plant. 

 V, Vegetative cone ; /, leaf rudiment ; g, rudi- 

 ment of an axillary bud. (x40.) 



form a BUD. Buds are therefore 

 If they are to remain for a long time 

 undeveloped, as for example is the case with winter buds, they are 

 protected in a special manner during their period of rest. 



The Origin of New Shoots. — The formation of new growing 

 points by the bifurcation of an older growing point, in a manner 

 similar to that already described for Didyota dichotoma (Fig. 8), occurs 

 also in the lower thalloid Hepaticae (lUccia fluituns, Fig. 10). Among 

 the cormophytes this method of producing new shoots is of less fre- 

 quent occurrence, and is then mainly limited to the Pteridophytes, 

 and is typically shown only in some Lycopodiaceae. In this case, 

 whenever a shoot is in process of bifiu'cation, two new vegetative 

 cones are formed by the division of the growing point (Fig. 18). 

 In most of the Lycopodiaceae the new shoots thus formed develop 



