T. Holm — Croomia j>auciflora. 51 



the mother-rhizome. Dormant buds may be observed in the 

 axils of some of the leaves of the horizontal portion of the 

 rhizome. The roots are white, somewhat fleshy and sparingly 

 ramified ; they develop mostly below the nodes or, sometimes, 

 a little above these. 



In the Japanese species C. Jajponica Mig. the habit of the 

 plant is the same, but the flowers are single in the axils of the 

 leaves, and the rhizome has no stretched internodes. 



The internal structure of the vegetative organs of our species 

 of Croomia shows several points of interest, when compared 

 with the allied orders, and we will begin with the roots. 



The roots. 



The secondary roots are storage-roots with no contractile 

 power ; they are nearly glabrous and the thin-walled epidermis 

 persists covering directly the cortical parenchyma, no hypo- 

 derm being developed. The cortex consists of about fifteen 

 layers of thin-walled, starch-bearing cells, constituting a rather 

 compact tissue. There is an endodermis of exceedingly small 

 cells with thin walls and the Casparyan spots barely visible ; it 

 surrounds a continuous similarly thin-walled pericambium. 

 Inside this are seven narrow rays of hadrome with one to two 

 protohadrome vessels and about twenty, much wider, around a 

 narrow central group of moderately thickened conjunctive tissue. 



The thin, lateral roots show a like structure, but the cortex 

 contains no starch and the endodermis is large-celled with the 

 spots plainly visible ; these roots were diarchic and the position 

 of the protohadrome vessels was like that in the mother-root, 

 inside the pericambium. 



The rhizome. 



When we examine one of the stretched, horizontal inter- 

 nodes we notice a smooth cuticle and an epidermis with the 

 outer cell-walls moderately thickened. The cortex consists of 

 about twenty-five layers, of which the peripheral two or three 

 are collenchymatic, the others thin-walled and starch-bearing. 

 No endodermis was to be observed, and the mestome-bundles 

 possess only a weak support of stereome, which does not form 

 a continuous ring around these. It is merely represented by a 

 few, one to two, layers on the inner face of the mestome- 

 bundles or on the sides of these ; on the leptome-side this 

 tissue is, also, poorly developed, sometimes entirely wanting. 



The structure of the mestome-bundles is very irregular. 

 They are apparently arranged in one or two circles, but several 

 of these having fused together so as to form several groups of 

 leptome and hadrome in immediate connection with each other, 

 their number or real position could not be ascertained. As 

 will be seen later, the mestome-bundles of the stem above 



