GROWTH AND ORIGIN OF MULTICELLULAR PLANTS. 259 
protoplasmic threads protruding through distinct perforations in 
the for the purpose of absorbing nitrogenous matter from 
Infusoria and mites which have perished in the cavity of the leaf. 
During the present season I haye again paid attention to this 
d am convinced that the cilia are extensions of a sheath 
external to the oetet ror behaves with reagents in a similar 
manner to the algal s 
e structures deneut as pits in the cell-wall are minute 
elevations of the sheath from which the cilia extend; perforations 
een 
Not unfrequently the eee of old eee of the sheath in alge, 
i is seen cove 
evidently due to unequal contraction of the substance of the sheath. 
This accidental ornamentation is suggestive as to the origin: of 
e always sm 
the true ae wall, The an soogae hordes or ee covering 
of sari -spores in Alge ungi o: ilar manner, 
ch has sade ‘a zagened ~~ Beigaoh * ‘for the resting- 
ate in the genus Acanthoco 
addition to the fctaneeas ‘of the external cuticularised sheath, 
a second function is performed by the substance exuded from cells 
in the interior of the thallus. In such genera as Caulocanthus, 
or aa Ceanens and Halymenia, the axis consists of one 
or more rows of large superposed cells, giving origin at intervals to 
ia or whorled branches, which, ne repeated hg hag 
form dense eyven- a sas corymbs in contact with each other; the 
cells, becoming s r outwards and agglutinated erry 959 
a cia fg ape a cortex. e resulting stru 
ture may be circular in section, as In Gloiosiphonia, or cipal 
often completely effacing the origin pk weseegntere: “These 
secondary growths usually re .smaller than pr cells, 
and are the cause of irr arity in aes De the cells, as seen in a 
us. 
In describing the structure of the Vos oe. Borzi+ remarks 
* «Ber. Deutsch. Bot. Gesell.’ iv. (1886). 
+ ‘ Malpighia,’ i. (1886), pp- 7483, 97—108, 145—160, 197203. 
