174 SUMMARY OF CURRENT RESEARCHES RELATING TO 



family Acanthacese, finds the mature plant to be astelic, not poljstelic 

 as stated by Holm. It has six peripheral meristeles, and one central 

 medullary bundle, each completely surrounded by an endodermal sheath ; 

 these anastomose at the nodes. The seedling is at first monostelic ; 

 the individual Inindles become gradually surrounded by the endodermal 

 sheath. The mature type with six bundles is derived from the seedling 

 type with four by the increase in size of the leaf -gaps. The axis of the 

 inflorescence is monostelic. The species differs from related forms in 

 tlie lack of interfascicular cambium, the individual bundles becoming 

 surrounded by endodermis. The medullary bundle is comparal)le to the 

 medullary bundles of AcantJms spinosus, many Campanulacege, and other 

 plants. It is probable that astely is merely a phase of monostely, the 

 endodermis being a physiological layer, the medullary and cortical 

 parenchyma becoming similar owing to like physiological conditions. 

 Astely in the species in question is probably correlated with its*aquatic 

 habitat. » 



Anomalous Stem-structure in Rochea.* — R. Hamet contributes a 

 note upon certain anomalies in the stem-structure of Rochea coccinea^ 

 and draws attention to the following points. The epidermis is composed 

 of^ a single layer of cells, the internal walls of which are slightly 

 thickened, and the external walls somewhat cutinized. The external 

 cortical tissues are composed of many layers of hexagonal cells, having 

 thin walls and triangular intercellular spaces, the latter being sometimes 

 replaced by collenchyma. The phloem is in more or less numerous 

 bundles, with occasional sieve-tubes, but no intercellular spaces ; the 

 xylem of these bundles consists of a few vessels embedded in paren- 

 chyma and without intercellular spaces. The pith is parenchymatous, 

 with many intercellular spaces. At each node there are two groups of 

 bundles, situated opposite to one another and outside the normal zone 

 of vascular bundles ; these anomalous bundles branch repeatedly, and 

 pass obliquely into the outer cortical tissues, but a median xylem vessel 

 and a few of the phloem elements from each, maintain a vertical position 

 and pass without l)ranching, as far as the next node, below which they 

 suddenly disappear. The structure of the leaf-stalk is identical with 

 that of the stem. 



^Reproductive. 



Life-history of Uvularia sessilifolia.f — Isabel Alden has studied 

 the development of the spores in this liliaceous plant, and tabulates the 

 following results. The archesporium and microsporangium, of from 

 three to six hypodermal cells, is differentiated in the first week in 

 August, when the hypodermal cells divide forming the primary sporo- 

 genus and the primary parietal cells. The latter divide several times, 

 giving rise to the wall of the sporangium and the tapetum ; the former 

 form several microspore-mother-cells which in October divide, forming 

 the usual tetrads. The microspores pass the winter unchanged, and in 



* Comptes Rendus, civ. (1912) pp. 1256-9. 



t Bull. Torrey Bot. Club, xxxix. (1912) pp. 439-46 (2 pis.). 



