126 ROBERT TRACY JACKSON ON 



In Chrysalidocnrpus Jutef<ce)is (Biuy) Wendl. [Areca Jufesceus Bury) (PI. 23, fig. 

 95), and Kentiti hfi/ntoreana (PL 23, fig. 9G), the seedling has first a simple distalh* cleft 

 leaf, succeeded in later growth l)y ])inuatel3' coni[)()uiid leaves, the distal end of which 

 resembles the first simple leaf. In the adidt the compound leaf has ninnerous leaflets, but 

 otherwise differs from the compound leaf as figured here only in the relative reduction 

 of the terminal leallet. Suckers of C'hriisaJklocavpKs httcsct^ns repeat the form of the 

 seedling so closely that they are practically identical in leaf characters. 



Fern.s. Ferns on account of their usually compound leaves should show evidences 

 of localized stages in development. While in higher plants the tip of the leaf is formed 

 first, and is early tiansformed into permanent tissue (p. Do), a different condition occurs 

 in ferns. In ferns the apical growth continues and in many genera is CA'en unlimited, 

 the apex being always capable of further growth (Sachs, '75). In spite of this radical 

 difference in method of growth, the tips of ferns are usually simpler than the i)roximal 

 portions and in so far they resemble the condition seen in the young. 



The individual leaflets of Adiantinn are similar to the whole frond of the vounsj:, 

 which in an early stage is composed of a single leaflet. The tip of the frond of OnocJca 

 seiisibilis L. is entire and in so far resembles the whole frond of the young, which is also 

 entire, though relatively broader and orljicular. 



A young plant of the connnon Brake [Pferis (iqii'il'ind L.) has a very simple type of 

 frond as compared with the iidult. Such a young S2iecimen, of which the frond is 6.5 cm. 

 high, is shown in PL 23, fig. 105. The distal tip of this frond is entire; passing jiroxi- 

 mally, the frond becomes pinnatifid and then once piiniate. The pinnae are themselves 

 distally entire, as is the tip of the frond ; but passing proximally they become iiinnatifid. 

 This plant, although young, shows the remains of several fronds preceding the one figured. 

 Somewhat older specimens have similar characters, but more advanced. The frond of 

 adult Pteris arpdlhin is twdce or thrice pinnate with three primary divisions. The simplest 

 parts of the frond are at the distal ends of the primary divisions, the most complex parts 

 are at the proxim;d ends of the same. The several divisions of the frond are entire at the 

 distal end, becoming more or less divided proximally. The distal end of the primary 

 divisions closely i-esembles the whole frond of the young plant (PL 23, fig. 1U5). 



Localized Stages in Development in Animals. 



Turning to the animal kingdom, there are some groups which i^resent interesting 

 ])hases of localized stages in development. In the asexual reproduction of animals by 

 budding, a new individual is produced in a manner which, roughly speaking, may be com- 

 pared to the reproduction of plants by suckers. Such youthful zooids one would expect 



