ivith Exhibition of a Rare Species (Cycas Micholitzii). 301 



specimen, having a diameter at the broadest part of 4 cm. and 

 rising to a height of 15 cm. above the surface of the soil, does 

 not appear consistent with the statement quoted by Sir William 

 Thiselton-Dyer from Mr Micholitz that the stem is subterranean. 

 The following extract from a letter written by Mr Micholitz* ex- 

 presses the views of the discoverer of the species on this point. 

 "The plant has its stem in the ground, that is to say the stems 

 grow downwards instead of upwards ; the stem of young plants 

 is covered with 3 — 4 inches of soil (precaution against heat and 

 bush-fires ?) and the older the plant the longer or deeper the 

 stem grows into the ground, so that the stem is never visible 

 above ground, and the flowering cones appear just level with the 

 ground." It would seem, therefore, that the species, as seen in 

 its native habitat, is characterised by the subterranean position 

 of the stem and that the aerial stem of the cultivated plant does 

 not represent the normal condition. The surface of the young 

 stem is covered by contiguous transversely elongated bases of 

 scale- and foliage-leaves, which do not exhibit that marked con- 

 trast in size characteristic of some other species of Cycas. A few 

 apogeotropic roots project above the surface of the ground close 

 to the base of the stem. The tip of the stem bears a few short 

 brown scale-leaves and two fronds. The petioles of the fronds 

 are long and slender, armed with a few short spines and termi- 

 nating in swollen bases : the margins of the enlarged bases are 

 winged and the wings extend a short distance up the sides of the 

 petiole as membranous extensions. The largest frond has a length 

 of 130 cm., measured from the tip of the uppermost pinna to 

 the base of the petiole ; the pinnae, reaching a length of 35 cm., 

 are either simple or divided almost to the base into two equal 

 segments. 



The vascular strand in the axis of a pinna exhibits the usual 

 Cycadean structure, but, as shown in Fig. 5, there is a considerable 

 development of centrifugal xylem. The main portion of the meta- 

 xylem, which consists of reticulate elements, has the form of a 

 slightly curved band (Fig. 5, cp): the somewhat crushed and 

 swollen protoxylem tracheids (px) form the pointed extremity 

 of a group of elements projecting upwards from the middle of 

 the upper face of the centripetal xylem. The space between the 

 centripetal and the centrifugal xylem is occupied by conjunctive 

 tissue composed of fairly large parenchymatous cells. The strand 

 is enclosed by a sheath (s) of crystal-containing cells with thick 

 lignified inner walls ; between the centripetal xylem and the 

 sheath occur 2 — 3 layers of parenchyma. The phloem shows the 



* I am indebted to Mi Lynch, the Curator of the Cambridge Botanic Garden, 

 for this extract, which he obtained through the courtesy of Messrs Sander and Sons. 



